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python	Pythonタグが付けられた新着投稿 - Qiita	Python: urllib3 で HTTP 認証 (Basic/Digest) する	https://qiita.com/yh1224/items/ad2c913865b1c6109bdf	basicdigest	2022-08-06 23:46:38
js	JavaScriptタグが付けられた新着投稿 - Qiita	【JavaScript && CSS】今更方向キーで丸を動かす	https://qiita.com/tacchan5424/items/cfe055525d20fc0415c6	ltdoctypehtmlgtlth	2022-08-06 23:26:26
技術ブログ	Developers.IO	Amazon Kinesis Data FirehoseでDynamic Partitioningによる出力データの動的パーティショニングを試してみた（AWS CDK）	https://dev.classmethod.jp/articles/dynamic-partitioning-of-output-data-using-dynamic-partitioning-on-amazon-kinesis-data-firehose-aws-cdk/	timestamp	2022-08-06 14:52:12
海外TECH	DEV Community	LinkedIn Jobs API	https://dev.to/eunit/linkedin-jobs-api-36m7	LinkedIn Jobs API OutlineIntroductionWhat you will learnWhat you can use LinkedIn Jobs API forHow to get access to LinkedIn Jobs APIGetting started with accessJob Posting CategoriesPosting job detailsLimitations of LinkedIn Jobs APIFurther readings IntroductionLinkedIn s Job Posting API enables authorized third parties such as clients ATS systems and job distributors to post jobs directly to LinkedIn on behalf of customers Jobs that are already created externally on ATS company site or job board can be automatically ingested by LinkedIn LinkedIn provides various solutions to ingest such jobs to your customers partner ATSs and Job Distributors What you will learnIn this article I shall walk you through understanding what LinkedIn Job Posting API is all about how you will integrate LinkedIn s Jobs Posting API to your ATS to directly post job openings to LinkedIn What you can use LinkedIn Jobs API forThe LinkedIn Job Posting API allows members who use it authorized third parties such as clients ATS systems and job distributors to automatically post jobs to LinkedIn from their Applicant Tracking System ATS instead of manually posting via their LinkedIn Recruiter account This API is typically utilized by recruiter clients who are currently using a job distribution tool It allows them people to post a job to various sites at one time including LinkedIn ATS partners no longer need login or password information to post on behalf of clients The LinkedIn jobs API in simple terms is used to publish jobs on LinkedIn on behalf of the hiring organization making it simpler for recruiters to find candidates who are a good fit for their open positions It is however important to point out that this feature is not available to Recruiter Online or Recruiter Lite accounts How to get access to LinkedIn Jobs APIThe use of LinkedIn s APIs is restricted to those developers approved by LinkedIn In order to get access to LinkedIn s Jobs APIs you will need to reach out to your LinkedIn Relationship Manager or Business Development contact as you will need to meet certain criteria and sign an API agreement with data restrictions in order to use this integration If you are not yet a LinkedIn Talent Solutions Partner please complete the LinkedIn Talent Solutions Partner Request Form here There are a number of restrictions or obligations you need to be aware of from LinkedIn These include but not limited to Acknowledging that LinkedIn acts as a passive conduit for the online distribution and publication of job listings and LinkedIn is not responsible for screening or monitoring job listings Jobs posted to the LinkedIn Service including via the LinkedIn APIs may be posted only for lawful purposes by individuals and employers seeking employees You will ensure that you agree to the LinkedIn Jobs Terms and Conditions prior to posting any jobs to the LinkedIn Service via partner s application and shall have a method of keeping track of which of its customers have agreed to the LinkedIn Jobs Terms and Conditions and when and shall furnish such information to LinkedIn upon request Shall not market any job listings to be distributed via LinkedIn or its syndication network as a free way to post jobs to LinkedIn or anything substantially similar in any marketing or sales materials Please refer to to a comprehensive list of these conditions here Getting started with accessYou must be granted access to test resources and have your API applications enabled to access the job posting API endpoints before you can start developing The actions listed below must be taken in order to seek access to use the LinkedIn Job Posting API For the integration create API applications Per integration you are allowed to create two API applications one for use in production and the other for testing and development Please contact the LinkedIn Business Development point of contact to fill up the Partner Onboarding Form Job Posting CategoriesThe following two job categories broadly define the ways to post jobs in LinkedIn Basic Jobs These are free job posts gathered by LinkedIn from external sources such as ATS job boards distributors and aggregators across the web to create a comprehensive job seeking experience for LinkedIn members Basic jobs can be posted using Job Postings API or XML feeds Promoted Jobs These are paid job postings You can directly post promoted jobs using Job Postings API For customers with paid job slots the API allows posting jobs directly into their job slots Posting job detailsTo create a job post the job by providing unique externalJobPostingId value and set the jobPostingOperationType as CREATE API EndpointUse the following endpoint to submit a task to create close update or renew one or more jobs asynchronously POST API AuthorizationAll requests below require access tokens obtained via the OAuth Client Credentials flow Sample Request for Basic JobsIn order to publish a job as a free job you need to provide listingType field value as BASIC API Header The header for making the request is X Restli Method batch create Authorization Bearer token x restli method batch createSample Request Body elements integrationContext urn li organization companyApplyUrl description We are looking for a passionate Software Engineer to design develop and install software solutions Software Engineer responsibilities include gathering user requirements defining system functionality and writing code in various languages Our ideal candidates are familiar with the software development life cycle SDLC from preliminary system analysis to tests and deployment employmentStatus PART TIME externalJobPostingId listedAt jobPostingOperationType CREATE title Software Engineer location India workplaceTypes remote integrationContext urn li organization companyApplyUrl description We are looking for a passionate Software Engineer to design develop and install software solutions Software Engineer responsibilities include gathering user requirements defining system functionality and writing code in various languages Our ideal candidates are familiar with the software development life cycle SDLC from preliminary system analysis to tests and deployment employmentStatus PART TIME externalJobPostingId listedAt jobPostingOperationType CREATE title Software Engineer location San Francisco CA workplaceTypes hybrid integrationContext urn li organization companyApplyUrl description We are looking for a passionate Senior Software Engineer to design develop and install software solutions Software Engineer responsibilities include gathering user requirements defining system functionality and writing code in various languages Our ideal candidates are familiar with the software development life cycle SDLC from preliminary system analysis to tests and deployment employmentStatus PART TIME externalJobPostingId listedAt jobPostingOperationType CREATE title Senior Software Engineer location San Francisco CA Limitations of LinkedIn Jobs APIThe LinkedIn jobs API is constantly evolving One of the biggest drawbacks of this API is that when you sign up as a developer to gain access to the API LinkedIn grants you a limit of API calls per day However if you run different scripts you will eventually get stopped after calls with an error stating that the throttle limit exceeds Meaning of throttlesAPI throttling is the process of limiting the number of API requests a user can make in a certain period To prevent abuse and ensure service stability all API requests are rate limited Rate limits specify the maximum number of API calls that can be made in a hour period These limits reset at midnight UTC every day There are three types of throttles applied to all API keys Application throttles These throttles limit the number of each API call your application can make using its API key User throttles These throttles limit the number of calls for any individual user of your application Developer throttles For people listed as developers on their API keys they will see user throttles that are approximately four times higher than the user throttles for most calls But your users will experience the User throttle limits which are lower These rate limits can be extended or the throttling limits can be increased to give developers more space to explore and build things for the user Further readingsLinkedIn API Products catalog Create Jobs LinkedInFollow me on Twitter eunit for more contents	2022-08-06 14:26:52
海外TECH	DEV Community	Grokking the Mobile System Design interview	https://dev.to/artem_goncharov_e0b3f99d2/grokking-the-mobile-system-design-interview-4ehm	Grokking the Mobile System Design interviewPurposeHow mobile system design interview usually looks likeCommon recommendationsProposed interview answer planBusiness ideaRequirements clarificationMathematical model design if needed High level system designAPI designHigh level client side designDetailed design of some modulesOne complex case and detailed discussionSummaryReferences Purpose Being a mobile developer you may know that it s a problem to find any preparation materials for mobile system design interview There are plenty of videos about backend system design interviews and just few of them about mobile one The same situation is with the articles one can find a lot of articles and even courses that would help to be prepared to the backend system design interview and there is no articles at all about mobile system design interviews That s why I thought it would be great to share my experience of the preparation and passing the mobile system design interviews Sure thing this article is just one way of grokking the interview and the outcome will depend not only on information you ve got from this article but on your knowledge skills and on interviews skills and knowledge as well so don t consider this info as a silver bullet How mobile system design interview usually looks like First let s explore how mobile system design interview looks like what are the input the process and the expectations ProcessUsually the interview takes about minutes minutes acquaintance minutes defining the task minutes solution minutes your questions to an interviewer Commonly your task is to design the mobile application or a part of the application and sometimes to design some part of backend that is relevant to the mobile application as well An interviewer lets you know all the needed information during the second minutes the input can vary from company to company InputLet s see what can be provided to you The idea of the new feature or of the whole application Usually it sounds like ー“Let s design the Instagram like application or “Given you work in Twitter let s add the the feature of combining some of your posts to stories Nothing more you commonly hear from the interviewer all additionally info you need to get from them using properly formulated questions ーthe technique will be described later in the article The sketches of the screens needed to implement the idea from the first item It s a very important piece of the information and you have to be very attentive in order to absorb all the nuances Some requirements and limitations like in what extent you need to design the system ーmobile only or mobile and API only or mobile and backend That s it no more input you most likely have from the interviewer ExpectationsHigh level expectations Ability to understand and solve complex problemsCommunicate clearly and effectivelyHaving relevant experience and knowledgeThe way of going deeper from this abstract definitions mainly depends on the interviewer theirs skillset experience and position in the company They can define complex problems very differently but we will try to formulate the most common concrete signals you should demonstrate For the first item in order to show your ability to understand and solve complex problems you should demonstrate the following Ability to think about the business part of the task as this is the first step in understanding the problem and answering the question “Why You would show the attitude to understand the business purpose of the feature or the whole application and apply this knowledge in the process of clarifying or generating the technical requirements Working well with the vague requirements The interviewer usually gives you very less information and this info is definitely not enough to even start designing thus you should be able to ask proper questions in order to clarify the requirements The requirements clarification process should be driven by definite and clear aims questions shouldn t be random but should rather follow some system Ability to synthesise the solution for a given problem In the first two items you demonstrated ability to understand the problem next step is to apply all the available knowledge and design a reasonable solution You would synthesise the design using the “top to bottom approach in order to provide the context and the main conceptions first and then using divide and conquer technics gradually split the system to smaller and smaller pieces The second item ーeffective and clear communication ーcould include Voice communication You should speak for about minutes without any big pauses explaining all your solutions and ideas with enough confidence knowledge and ability to defend your ideasWhiteboard communication A whiteboard is super helpful to document all your thoughts so you can return back to any step and see what you decided earlier and whether all of your decisions are consistent With regards to the relevant experience and knowledge Have experience in the development of the huge mobile applications or better the whole client server systems You are expected to show the knowledge of the application to server communications design one way two ways API design pagination cache and state management modularisation techniques different mobile application design patterns and their pros and cons In addition here you can demonstrate knowledge of the most popular problems in mobile apps and methods of avoiding them like state mutation storing of the big images in the app state and overuse of singletons and god objects Ability to foresee the problems or difficulties in the solution Some solutions can be very hard to implement and you are expected to clearly communicate about it explain where the possible problem or the trade off is Have experience working with the different quality assurance and risk mitigation techniques Here you are expected to mention how you make your design good for testing blue green deployments fail fast etc Ability to design the modules on the class level awareness of the main principles and design patterns Very unlikely you will have time to do this but still there is a chance the interviewer will ask you questions like “How would you implement updating of the unread messages count label ーyou will need to decide will it be observer pattern or delegate or polling or whatever else it could be and draw the simple diagram Common recommendations Summarising the most popular recommendations companies provide before the interview You need to gather as many requirements as possible from your interviewer before starting designing Don t hesitate to ask as many questions as needed You should show your knowledge so it s possible to start from the part of design you know the best You shouldn t be silent speak all the time communicate clearly don t wait for hints from the interviewer Always provide information about the alternatives and defend your choice Proposed interview answer plan I believe that if in your company you have a good tradition to do a design review before implementation of any big or cross team feature you can notice that actually a system design interview looks like a complex design review along with the preliminary work when you gather the requirements think about the design and draw diagrams So you can conduct design review for times and it should be enough to understand the idea But if you don t have such an option let s explore the good plan of your system design interview This could be the high level plan Business idea what we are selling to user usually it s the services and the data minutesRequirements clarification dimensions to help with limitations minutesDesigning of a mathematical model if needed minutesDefine how to split that state and functionality between the server and the client sides minutesAPI design minutesHigh level client side design layered structure minutesDetailed design of the one chosen module minutesOne complex tricky case and detailed discussion minutesLet s explore each item from the below plan in more detail Business idea This is mainly to understand the context to formulate what exactly we are going to sell users what kind of services and data and to start thinking about the task from the very top The outcome of this step is as the following The list of services we sell to our usersThe data entities access we sell to our usersUnderstanding the main idea of the product or the feature if you don t understand something don t hesitate to ask all the needed questions The more you know about the product the easier will be making decisions during the the rest of the process For instance if you were asked to design the simplified WhatsApp like application without registering login groups broadcast lists EE encryption and reading the status then the outcome of this step would be something like this We sell the following services Safely storing and providing read write access to your address book Providing the ability to make receive Audio and Video calls to contacts from your address book Providing the ability to send receive text messages and images to contacts from your address book and safely store the history of all the chatsServices should be as independent from each other as possible so it will help you to design API faster In our example all services depend on address book service but they are independent from each other We sell the access to the following data Address book item First name Family name Phone numberChat history message User opponent Inbound or outbound Date and time of the message Message text or ImageSo the above services list and the data entities UI sketches commonly provided by the interviewer form the basis for all your future work The data entities are not the final ones and are not prepared to be stored or transferred by network it s just a high level description of the data mostly from the end user perspective You can start clarifing requirements right here for instance you can ask whether we need to add user avatar image but in this case you should be ready to answer this question by your self since the interviewer can ask you back the same question and you should reason your choice Requirements clarification It s very important to gather all the possible requirements beforehand We started doing that with the business requirements on the previous step now we need to clarify the technical requirements the limitations and the context Why do we need it Because your design should depend on the context development processes and actually the ask from the customer PO interviewer So the first question should be about the context whether we have any in our task whether we have the host application we re adding new functionality to whether we have backend already done for the web version how big our team is and what their expertise is In of the cases I believe the interviewer will answer that there is no context at all and you should start from the scratch but these questions will show that you do care about the context and take it into account during the solution design process Concerning the limitations I prefer to use a checklist for evaluation of the design solutions The following list contains the checklist items and questions that can be asked regarding each of the item related to the mobile system design You can come up with different questions and use another list this one just for reminding you of the questions during the interview Maintainability ーare we designing MVP or PoC or full scale system How big is the team which will implement my design Testability ーwe can leave this dimension we definitely need to think about some type of testing No limitations here just not to forget to mention about testing on the latest steps of you design Scalability Performance ーhere we can treat scalability as the scalability of our team ーability to reuse their code in different platforms and though we can ask about cross platform option since it can impact our design considerably Also you can ask questions about some parameters that could impact the performance of the applications where performance is crucial and where it s better to define limitations beforehand For instance if you are designing an application with recognition of many objects in the live video using ML you could mention that we limit our selves to the latest models of Android or iOS devices only Otherwise we need to use third party libraries and use main processor for making all the calculation that can affect the battery life and the quality of recognition This will not impact design so seriously but it s worth mentioning since it shows your experience and an ability to foresee the problems Security ーit s very important to discuss the limitations caused by security reasons Especially if you re asked to store some information on the device or if you should work with the Personally Identifiable Information PII or sensitive PII So it s better to clarify with the interviewer that persisting and transferring requested information should be safe and if you think it s not safe you should suggest what have to be done to protect it Availability ーhere we can ask about the ability to work offline probably limitations of OS versions phone tablet choice using limited set of languages and screen sizes Of course all those questions should be asked only if it s relevant to your task There is no need to enlist all the dimensions on the whiteboard as they work only as the keys to recall what should you think and ask about Later on you can use the same dimensions if you will be asked to compare two solutions It s better to write all the answers to the above questions on the whiteboard so you can reference them later Mathematical model design This step is relevant only to a limited subset of the tasks Those tasks would sound like following You are a Facebook developer and you have to add new feature to show the two most popular posts at the top of the feed In this case you need to clarify come up with what it means ー“most popular and then describe how you can calculate it should you use views or comments or likes in order to figure it out should it be instant popularity or moving average and so on You are a developer in a rapidly growing super hotel aggregator and your task is to develop a bot detection feature Here you should define the input data you need to detect bots and come up with the algorithm and mathematical model of how to use this data in order to distinguish bots from the real users For instance you can calculate the requests rate using moving window and compare it to a given limit Outcome of this step would be a simple schema of the module with inputs formula s inside and outputs High level system design Next step is to decide what part of the services and the data should be implemented stored on the server and what part should be implemented stored on the mobile device Here you can use the output of the first step ーlist of services and data entities Let s consider previous example ーWhatsApp like app Can we implement address book storage on device only No because we need to have one shared store so all the clients can use it in order to be able to contact to the needed correspondent We don t consider distributed storage schemes but you can think about it and compare with the above schema using dimensions from the second step Can we implement Audio calls using client side only Yes but you need to let the interviewer know about all the tradeoffs in that case in comparison to the server side service like EE encryption better scalability worse availability because of NAT traversal and so on For instance you decide to put all the services to the server side and so all the data will reside on the server as well Then since all the data and services reside on the backend we need to choose the client server communication type for each of them one by one For WhatsApp like application example address book service can be easily implemented as a simple REST HTTP calls with JSON payload given that each user can use only one device and so we don t need server to client notifications about changes in the address book contacts Audio Video calls service would use its own communication interfaces ーbidirectional TCP based connection for a signal protocol WebSocket probably and UDP based for the streaming of the data RTP probably On this step it should be enough to just mention type of communication bidirectional or unidirectional streaming or request response based then more details ーHTTP REST simple long polling web socket raw socket etc… For the text images chats service it is a bit harder to decide what communication channel to use It could be REST HTTP push notification or bidirectional web sockets or custom TCP based channel or something else All the options have their own pros and cons so you can choose any option just let the interviewer know about the other alternatives and be ready to defend the chosen one The outcome of this step should be something like on the following scheme where you define the place where the services and the data will reside communication channels between the server and clients This is the first very high level structure of our system and most likely it will be the only scheme where you draw any backend details API design This topic is rather controversial there are a lot of ways to design the API so you can use any of them the only thing is to define all the exact data entities and API calls as an outcome of this step Side effect of API design is the clarification of some server side solutions From my experience it s good to start from the service and the data entity that other services data entities depend on and expand it to one or more API calls For instance our first service is address book so there would be API calls GET address book page limit gt AddressBookItem Read the address book data with paging it s very important not to forget about paging ーbetter if you consider paging by default to any call and then remove it if it s not needed than to forget about it at all I intentionally don t mention any user identifier as we need to mention in the interview that all the requests should contain header with authorisation token which was received earlier during login procedure If the interviewer wants to know more about login you can let him know one or more ways of the register login implementation POST address book user id first name family name phone gt AddressBookItem Add new record to the address book PUT address book usert id first name family name phone gt AddressBookItem Update existed record in the address book DELETE address book user id Delete existed record from the address book Where AddressBookItem looks like AddressBookItem user id int first name string family name string phone stringRead chat message API call would look like GET chat history user id page limit gt ChatMessage ChatImageMessage Where ChatImageMessage looks like ChatImageMessage user id int msg id int dt timestamp is inbound bool img url thumb string img url full size stringI wrote API calls in a custom form that is easy to show in one line so question mark doesn t mean we will use request path parameters it s just delimiter between the call name and parameters list Moreover word “GET doesn t imply we will use HTTP requests it could be WebSocket according to our high level scheme and this API call can be encoded with Google Protobuf for instance but idea will remain the same ーit should be an idempotent call with three input parameters that returns array of types of chat messages simple text message and image message You can come up with your own format of writing API calls if you think it would better represent the call name input and output data At this step we define data with more details taking into account server side implementation and trying to foresee future problems For instance we added unique identifiers to users and messages and represent image as two direct links ーone for a thumbnail and one for a full size image Most likely in your task you will have to work with images so it s better to think about the possible problems beforehand like saving a lot of traffic for users by downloading only thumbnails and not the full size images It sounds obvious but those small optimisations make your solution more interesting to design and discuss Designing an API is an iterative process you can change API later when you will be designing client side and it s OK This step is rather important and hard since you need to think simultaneously about server side design and client side design trying to foresee future problems with the connection speed throughput and usage convenience The previous steps are intended to prepare you by providing with the services list data entities and the type of communication channel between the client and the server After finishing this step you can spend some time analysing the result ーprobably there are some obvious optimisations you can apply to the API for example you may want to merge some APIs to one or split some of them or even decide to change communication channel because for instance it turns out that bidirectional communication better suits for one of the cases High level client side design Finally you can start drawing the client modules structure scheme Layered design commonly the easiest way to organise modules in some meaningful groups in almost all Frontend applications It s better to start drawing this scheme from the central and most important part of it ーthe state and services that doesn t related to sate These are things you provide to your users so let s start designing from them You can name this layer business entities or Business Layer and then start going downwards in order to meet the server side The next layer could be Service Layer here I use name “service in a different meaning than beforeーinterval Services Layer helps to isolate concrete implementations of the low level communication and persistent modules Data Layer from the Business Layer So Business Layer shouldn t bother about the place where we get the data from ーpersistent storage or communication channels and what kind of SDK we use to implement audio video calls Another purpose of the Service Layer is to convert data from multiple formats to the one Business Layer is using At this step we don t make any assumptions about implementation of the services ーwill it be the set of middleware in Redux or services distributed among VIPER modules or something else we can just mention that our purpose is to make services stateless and to try to keep explicit state in the Business Layer only Data Layer contains SDKs frameworks libraries that provide your application with such features like network communication local DB access logging or complete fully functional features like Audio Video calls Of course you can split Data Layer to multiple internal layers if it makes sense for instance if you develop some low level codecs you would have two layers in the Data Layer ーone for high level orchestration and one for low level access to device hardware but it should be hidden in the Data Layer and exposed only in Dependency Injection phase where we can define what kind of modules and codec should be used in Data Layer Going upwards from business layer to meet user we should draw the Presentation Layer The main purpose of this layer is to prepare the data from Business Layer to be displayed to user in UI Layer Again it worth to mention that we want to keep the Presentation Layer stateless The last layer to draw on the high level design structure scheme is UI Layer It s a very platform specific layer where the business data converted by the Presentation Layer is being displayed on the device screen using OS SDKs The second purpose of this layer is to interact with the user and pass all those interactions throughout the Presentation Layer to the Business Layer and further if needed This layered design can be mapped to any concrete architecture patterns like MVC MVI Redux VIPER RIBs etc but it s very important to remain on the higher level of abstraction at this step and not to go deeper to those concrete patterns You can mention such thing like “module here but postpone the concrete definition of the “module to the next step as module s meaning depends on the architecture pattern you will choose later for instance module in VIPER lays horizontally and crosses all the layers except the Data Layer so each module contain small piece if each layer In opposite Redux usually doesn t have modules but more like features instead Detailed design of some modules Here we should finally choose one feature module and define the architecture pattern that suits it best in your opinion Let s consider the chat feature in a WhatsApp like application As the chat feature crosses all the layers the chosen pattern will influence the whole application so we need to think not only about chosen feature but rather about the app in a whole Actually our WhatsApp like application works with rather limited types of data entities that are related to each other and all changes in the data should be immediately reflected in different part of the application as messages in the chat list and the chat screen as a notification when user browses the other parts of the app and as a counter of the unread messages It means we can have the one periodically updated state with the ability to subscribe to those state s changes Looks like Redux is a good option for the Business Layer middleware as the Service Layer MVP or MVVM or MVI patterns for the Presentation and UI layers with the Redux store playing the Model role VIPER seems a bit excessive for just a few screens with minimum number of routes between them and RIBs is better suits very complex screens with many teams working on the same screen Of course you can choose any pattern or mention none of them but then you would have to to explain where store state should be placed how it should work how we would implement subscription for state changes how services should be used and how they will update the state I intentionally didn t mention any concrete platform as it actually doesn t matter if it s Android or iOS as there are multiple implementations of Redux store and reactive frameworks for implementation of the MVVM MVI for both platforms whereas MVP doesn t need any Let s draw a possible structure scheme for the chat feature Here it s important to describe how all the cycle of the data update would work demonstrate the advantages of the pattern you have chosen and mention some tradeoffs and hard problems you would encounter during the implementation of this solution For instance we can enlist the following advantages of the chat feature s Redux design using the previous dimensions Maintainability We fully decouple data receiving part Data and Service Layer and data consumer part Presentation and UI Layer using store with updates subscriptions so it doesn t matter from which source the data comes ーfrom a persistent store or a network communication channel It helps to change some parts of the app without impacting the others reuse as much code as possible Scalability The store could have multiple subscribers out of the box so Presenter of our chat feature will be triggered and will pass the latest changes to View in order to display them Presenter of the top panel for instance will be triggered as well and will update the counter of the unread messages Adding one more subscriber is easy Testability State is immutable and located in one place not distributed across the app which help to avoid many mistakes related to simultaneous changes of the state Also it helps to test the app as you are sure that state can be changed only in reducers Disadvantages Deployability and partly Maintainability complex project structure and the tricky modularisation concept In order to change something in the chat feature developers will have to make changes in many places ーstate reducers actions middleware Presenter View Moreover all those places are spreader among the project we can come up with a project structure that minimise this effect by uniting the most of the parts in one place but it could lead with the repeating code and problems with changing the other teams code which makes modularisation a bit tricky So every team will be most likely touching the store state and it means rebuilding of all the modules as all the modules depend on the state Scalability the bigger become the application the bigger become the state Usually we split it into sub states so each feature has it s own sub state but anyway huge state could lead to performance and multithreaded access issues It s worth mentioning that your pattern approach design is good for testing for instance in our example we can mention that we should test middleware services presenters and reducers and it s very easy since they are stateless Additionally here you can demonstrate the skill of class diagrams designing Specific implementation will depend on the platform because for instance table rendering concepts are different in Android and iOS One complex case and detailed discussion At this step you can show the knowledge of the platform and problem solving skill It s better to choose one interesting case that you met before and successfully resolved and softly lead the conversation to this case For instance you can say that it s interesting problem of caching the images in the chats Each image has direct link to it s thumbnail and full size image and once image comes to the visible area of the screen it will be requested from let s say an image download service which downloads image using those direct links Weak point of such a solution is that if user has slow network connection images will appear too late especially if user scrolls chat rather fast Obviously we need a cache The easiest solution is to add to the image download service a memory cache which represents the dictionary with keys as direct links and values as images but what will happen when we restart the app All the text messages will be restored from the local DB assume it but should we save thumbnails and full size images in DB as well Or should we save only thumbnails in DB and full size images in the file system If we will save images in the filesystem how can we find them later on How can we housekeep folder with images if for instance device in case of iOS asks to free some space up There are a lot of questions and answering them could demonstrate your experience knowledge of the platform and problem solving skills So the trick here is to choose one common hard enough problem beforehand and lead the conversation to this problem The interviewer can reject that and choose the random one but still you will show that you aware of some problems and you would have a chance to talk a lot about the problem you know the best Summary Summarizing the above information I can say that it s always better to elaborate a plan of the common system design interview beforehand should it be like one I suggested in this article or another one It doesn t matter which plan you will chose but it should clearly demonstrate your ability to tackle a very big ambiguous problem ーsplit it to some meaningful pieces absorb them one by one process that information and produce another type of relevant information as an outcome Good luck at your interviews and don t hesitate to write comments to this article or share your experience References Layered architecture pattern Architecture systems quality attributes dimensions There are a lot of books about API Design it does worth to read at least oneMobile Architecture patterns MVC MVP MVVM MVI VIPER REDUX etc It would be good to know about them and about the conceptions behind each of them even if you don t want to mention any of them on the interview It s easy to find a lot of info about each of them	2022-08-06 14:21:59
海外TECH	DEV Community	How to connect your flask application to AWS RDS with a CI/CD pipeline	https://dev.to/programmingwithalex/how-to-connect-your-flask-application-to-aws-rds-with-a-cicd-pipeline-1cll	How to connect your flask application to AWS RDS with a CI CD pipelineIn this video I go through Creating an AWS RDS instance with PostgreSQLModifying a flask app to connect to the RDS instanceSetting up pgadmin so you can interact with the database server locallyCI CD pipeline with GitHub actionsAll the code for the video is on GitHub as well with the link in the video description This video is the latest in a longer series where I detail the steps necessary to take a local hello world flask application from your local machine to AWS so you can access via a domain name You can find the full playlist hereIf you find the video helpful you can greatly help me by doing one or all of the following supporting me on Patreonsubscribing to my YouTube channelliking and or commenting on the videosharing the video or channel on any platform reddit twitter discord etc starring the GitHub repofollowing me on GitHubAny questions or requests just leave a comment	2022-08-06 14:02:06
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