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soumik-saha/README.md

Soumik Saha β€” Backend Engineer | Java Β· Spring Boot Β· System Design

LinkedIn Portfolio Email profile views


What I Do

  • Design and build REST APIs with clear contracts, layered service boundaries, and explicit error handling
  • Apply correctness-first patterns β€” idempotency keys for deduplication, pessimistic locking for concurrent writes, and audit trails for observability
  • Structure Spring Boot applications with separation of concerns: controller β†’ service β†’ repository, with profile-based config for dev/prod parity
  • Decompose systems into cooperating services: Java backend + Python microservice + Helm-based Kubernetes deployment (see Briefly)
  • Integrate security at the infrastructure layer β€” custom JWT filter chain, role-scoped endpoints, and admin registration gated by a shared secret header

Tech Stack

Backend Java 17 Β· Spring Boot 3.x Β· Spring Security Β· Spring Data JPA Β· Python 3 Β· FastAPI Β· Node.js Β· Express.js

Databases PostgreSQL Β· MySQL Β· MongoDB Β· H2 (testing)

Infrastructure & Tools Docker Β· Docker Compose Β· Helm Β· Kubernetes Β· Maven Β· Gradle Β· Git Β· Caffeine Cache


Featured Projects

Production-grade e-commerce REST API β€” cart, checkout, order lifecycle, payments, returns, audit trail.

Engineering Highlights

Area Decision
API Design Role-scoped endpoints (USER / ADMIN); admin registration protected by X-Admin-Secret header to prevent privilege escalation without a separate admin service
Authentication Custom JwtAuthenticationFilter injects principal before the security chain; access + refresh token pair with configurable expiry; 401 / 403 handled by dedicated entry points
Database PostgreSQL (prod) / H2 (test) via Spring profiles; findByIdForUpdate (pessimistic lock) on product rows during checkout prevents oversell under concurrent requests
Idempotency Order creation checks for an existing idempotencyKey before inserting β€” a duplicate POST returns the original order, not a second charge
Async processing Order confirmation dispatched to a dedicated notificationExecutor thread pool via @Async β€” API response is not blocked by downstream notification latency
Caching Caffeine in-process cache with the Spring Cache abstraction; designed to swap to Redis by changing a single dependency
Audit logging Batch audit upload with per-entry idempotency keys; successCount / duplicateCount / failureCount breakdown; filterable CSV export for admin review
Observability AOP-based request/response logging; order and payment status history tables capture every state transition with timestamps
Ops Multi-stage Docker build; Docker Compose starts app only after pg_isready healthcheck passes; environment secrets injected at runtime, not baked into the image

Impact Full e-commerce lifecycle in a single deployable unit: auth β†’ catalog β†’ cart β†’ checkout (with promo codes) β†’ order tracking β†’ return requests β†’ audit export. Documented via Swagger UI.


Multi-service URL summarization app: Spring Boot API + FastAPI LLM microservice + React UI, deployable to Kubernetes via Helm.

Engineering Highlights

  • Service decomposition: Spring Boot (Java/Gradle) owns API routing and summary persistence; FastAPI (Python) isolates LLM inference β€” two runtimes, each independently scalable and replaceable
  • Deployment: Helm chart for Kubernetes; root-level Docker Compose for local parity; each service ships its own Dockerfile
  • Separation of concerns: The Java backend treats the LLM service as an internal dependency β€” callers never talk to the model server directly

Impact Demonstrates polyglot service design and cloud-native deployment readiness beyond a single Spring Boot monolith.


Automated aircraft damage detection system β€” built for Airbus Aerothon 6.0.

Engineering Highlights

  • Fine-tuned YOLOv5 on a custom aviation dataset (Roboflow) to detect and localize cracks, dents, and deformities on fuselage and wings
  • Random Forest classifier trained on image-extracted features to flag faulty wiring within aircraft harnesses
  • Streamlit backend integrates model inference with file upload, result visualization, and repair recommendation output
  • End-to-end pipeline: image upload β†’ preprocessing (OpenCV) β†’ damage classification β†’ repair suggestion

Impact Working prototype delivered under hackathon time constraints; covers the full detection-to-recommendation loop for three damage categories.


Blood donation matching platform connecting donors, recipients, and blood banks.

Engineering Highlights

  • JWT + Google OAuth2 via Passport.js β€” local and social auth strategies, session-aware cookie handling
  • MongoDB/Mongoose schema design for donor profiles, donation requests, and bank inventory
  • Express middleware chain: CORS β†’ cookie-parser β†’ auth β†’ route handlers

Impact Full-stack MERN application with dual auth strategies and geo-aware donor matching flow.


Engineering Mindset

I start with correctness before optimizing for performance. That means: define the contract, handle the failure modes, make operations safe to retry, then add caching or async paths where the profiling justifies it. I prefer explicit over implicit β€” if a service has a side effect (audit log, notification, stock decrement), that effect is visible in code, not hidden in an interceptor with no obvious trigger.


Current Focus

  • Distributed systems fundamentals: consensus, replication, and partition tolerance trade-offs
  • High-level and low-level system design (rate limiters, notification fan-out, distributed queues)
  • Deepening Spring ecosystem knowledge: reactive streams, Spring Batch, Spring Cloud patterns

Contact

LinkedIn linkedin.com/in/soumikisonline
Portfolio www.soumik.co.in
Email sahasoumik1573@gmail.com
GitHub github.com/soumik-saha
LeetCode leetcode.com/soumiksaha

Profile Notes (for reviewers)

Repositories not worth your time: DN3.0_Exercises (training coursework), CrackYourPlacement / 6-Companies-30-Days (DSA grind repos), Number-Guessing-Game, Rock-Paper-Scissor, Simon-Game, dice-challenge, drum-kit (toy/tutorial projects), tindog, Space-Tourism, EliteTask-Dynamics (HTML/CSS clones with no backend).

High-impact projects I'm building next:

  1. Rate Limiter Service β€” token bucket + sliding window, Redis-backed, exposed as a library and as a standalone gRPC endpoint
  2. Distributed Task Queue β€” delayed job scheduling, priority queue, at-least-once delivery with retry/backoff, worker pool management
  3. Real-time Notification System β€” SSE + WebSocket fan-out, subscription management, delivery guarantee with inbox persistence

Pinned Loading

  1. PulseConnect PulseConnect Public

    PulseConnect: Simplifying Blood Donation. Connects donors, recipients, and blood banks seamlessly. Register, request, or organize donation camps effortlessly. Secure authentication ensures trust. J…

    JavaScript 1 1

  2. flight-management-system flight-management-system Public

    JavaScript 1

  3. LearnHub LearnHub Public

    JavaScript

  4. SkyPulse SkyPulse Public

    An automated system using image recognition and machine learning to detect and classify aircraft damage, predict repair methods, and improve maintenance efficiency.

    Python 3 3

  5. EliteTask-Dynamics EliteTask-Dynamics Public

    This is a service based company's website.

    HTML

  6. Book-Store Book-Store Public

    This is an Book Store web application which is created by using MERN Stack.

    JavaScript