akashchouhan16 / potd-node.js-service

:gear: Node.js Service for POTD Chrome extension.

Problem Of The Day | Node.js microservice

A Node.js microservice to power the problem of the day Google Chrome browser extension. The POTD browser extension beta release is available for download on @Github/Hack-Repository.

Download Beta version from Github: Download

About

The POTD service caters to bring consistency into the young budding computer science students and enthusiasts towards DSA coding challenges. The idea here is to provide an easy to plug chrome browser extension to the users. Users are exposed a daily practice problem, which are from a pool 750+ problems, curated by software engineers from Google & Directi.

The Curated selection of important coding interview questions were hand-picked from existing lists that includes but are not limited to Striver's SDE Sheet, 450 DSA Sheet, and many more. The extension is presently available as a beta release to generate user feedback, and is not yet available on the Chrome Store.

• Server uses the Cache-First policy to prevent network requests to DB, by interacting with the in-memory cache if the problem has already been requested by the client, or makes a network request to a private collection deployed on Mongo Atlas Cloud DB.

Updates: v1.0.3

• POTD ContestsAPI: Get Access to all upcoming global contests on platforms including KickStart, Codeforces, AtCoder, Codechef, LeetCode and more.
• Faster Load Time: Optimized load times with both client-side & server-side data caching and storage.

About POTD Client

• It a Google Chrome Browser extension to provide a daily practice problem statement and problem link.
• Get Latest Contest updates from Platforms like Google Kickstart, Codeforces, AtCoder, LeetCode, and more.
• Browser extension is available to download and is released as v1.0.1-beta on Github.
• Stable version to be released on the Chrome Store after generating user feedback.
• Extension Preview:

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System Architecture (High Level Design)

• Below is the DFD for the v1.0.0 of the POTD service.

Note: Design has undergone multiple changes to incorporate Client and Server side data caching and storage options since its inception.

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Application Details

Version

v1.0.3

Maintainer

Akash Chouhan

License

MIT

All rights reserved. Copyright (c) @POTD/Akash Chouhan.

potd-node.js-service's Issues

To update Problems on a recurring basis, using a random iterator.

• The Problem Of The Day should be picked randomly from the DB, instead of sequentially.
• Updates should be scheduled on a recurring basis using Cron.

Migrate Instance from Heroku

• Current version is running on Heroku's free tier instance
• Migrate to DigitalOcean droplet or any low-latency deployment service.

To add caching to reduce the number of network requests to the DB.

• Currently, the server makes a query to the DB with the iterator value to fetch the problem of the day, for every request made by the client on /problemoftheday.
• This is not at all scalable and it also leads to very high latencies to process each request. Caching the problem of the day to the server memory itself with the first request. ~600-1200ms. Further get requests made by the client could directly access the problem of the day from the server cache, hence reducing latency to less than ~50-60ms.

• Add Caching onto the server, to avoid network requests to DB for every client-side request.

To add multiple instances on the server to process POTD Client's Request

• The server should utilize multiple CPUs if present on the system, to run concurrent requests.

Note: Could be achieved with cluster & os module in Node.

Local Error : NODE_ENV needs minor fix to prevent build fails on Heroku Instance

Introduce Rate Limiter

• Implement API rate limiter for /problemoftheday api
• Expected Config

const limitConfig = {
    windowMs: 5*60*1000,                    // 5min window
    max: 7                                 //max no of requests per window
};