SonoCode-Coding-Platform-Backend

SonoCode is a high-performance, distributed coding platform inspired by LeetCode, built with advanced microservices architecture principles. This project demonstrates enterprise-level backend development concepts including event-driven architecture, asynchronous processing, real-time communication, and tackles advance system design problems.

System Design & Data-Flow

The architecture is a decoupled, event-driven system where the Submission Service acts as the primary ingress point. Upon receiving a request, it persists an initial state and publishes a job to a Submission Redis Queue. A separate Evaluator Service worker consumes this job, spins up a secure, isolated Docker container for sandboxed code execution, and upon completion, publishes the results to an Evaluation Redis Queue. The Submission Service is also subscribed to this queue, and upon receiving the result, it updates the database and pushes the final payload to the WebSocket Service, which relays it to the client for asynchronous, real-time feedback. This design ensures non-blocking I/O, high throughput, and resilience by decoupling the API from the resource-intensive evaluation logic.

🔑 Key Highlights:

Feature	Description
Distributed Microservices	The platform is built as a collection of independent, domain-driven services (Problems, Submissions, Evaluation, Sockets).
High-Performance API Framework	The Submission Service is built using Fastify, a low-overhead web framework, to handle a high volume of incoming code submissions efficiently.
Redis-Powered Message Queues	Utilizes Redis as a message broker for asynchronous task handling between the submission and evaluation services.
Async Pub/Sub Model	Implements a publisher/subscriber pattern using Redis for broadcasting events and state changes across the system.
WebSocket for Real-Time IO	Employs WebSockets for persistent, bidirectional communication, providing instant feedback on submission status to the user.
Scalable Session Management	Uses Redis as a distributed cache to store user-to-socket-ID mappings, enabling stateful connection management across multiple Socket Service instances.
Dynamic Docker Container Factory	The evaluation service dynamically creates and manages isolated Docker containers for executing user-submitted code securely.
Secure Execution Sandbox	Leverages Docker to create a completely isolated environment for each submission, restricting file system, network, and process access.
Resource Exhaustion Mitigation	Imposes strict resource limits (CPU, memory, process count) on each Docker container to prevent attacks like fork bombs.
CI/CD & Shell Automation	Leverages shell scripting for service configuration, build processes, and deployment automation.
Resilient & Fault-Tolerant Design	Asynchronous communication and service decoupling inherently make the system more resilient to individual service failures.

📦 Repository and Service Links

This section maps out each core microservice and its corresponding repository.

Service Name	Description	Repository Link
Submission Service	Acts as the primary API ingress, handling all incoming code submissions and orchestrating the workflow.	SonoCode-Submission-Service
Evaluator Service	A background worker that consumes jobs from the queue and evaluates code in a secure, sandboxed Docker environment.	SonoCode-Evaluator-Service
Socket Service	Manages persistent WebSocket connections for pushing real-time evaluation results and status updates to clients.	SonoCode-Socket-Service
Problem Admin Service	Handles all CRUD (Create, Read, Update, Delete) operations for managing coding problems and their test cases.	SonoCode-Problem-Service

🗃️ Database Schema

The project uses two main MongoDB collections: problems and submissions.

1. problems Collection

Stores all data for a single coding problem.

Field	Type	Description
_id	ObjectId	Unique problem ID.
title	String	Problem title.
description	String	Full problem statement.
difficulty	String	Difficulty level (e.g., "easy").
testCases	Array<Object>	Array of {input, output} objects for validation.
codeStubs	Array<Object>	Language-specific boilerplate code.

View example document

{
  "_id": { "$oid": "68ac63e7823a7a68037ca1e0" },
  "title": "Valid Palindrome 3",
  "description": "A phrase is a palindrome if...",
  "difficulty": "easy",
  "testCases": [ { "input": "race a car", "output": "true" } ],
  "codeStubs": [ { "language": "CPP", "startSnippet": "...", "endSnippet": "...", "userSnippet": "..." } ]
}

2. submissions Collection

Stores a user's code submission for a specific problem.

Field	Type	Description
_id	ObjectId	Unique submission ID.
userId	String	ID of the user who made the submission.
problemId	ObjectId	Foreign key referencing the problems collection.
code	String	The user's submitted source code.
language	String	Language of the submission (e.g., "CPP").
status	String	Current status (e.g., "Pending", "Success").

View example document

{
  "_id": { "$oid": "68ac61b251ed0b4484ff9a20" },
  "userId": "1",
  "problemId": "68ac2d20c2911d94596215cb",
  "code": "class Solution { ... };",
  "language": "CPP",
  "status": "Success"
}

🚀 Test My Backend

You can test the entire code submission and evaluation workflow — from submitting a solution to receiving real-time results — using the Postman collection linked below. This collection includes all available API endpoints across the SonoCode microservices.

🔗 Postman Collection: [Insert your Postman link here]