Production agritech marketplace connecting farmers, buyers, traders, FPOs and agribusinesses. I built a server-driven UI template system (Flutter + Firestore, versioned templates, dev→prod promotion, one-tap rollback) and the customer app's registration, auctions, marketplace and mandi-price flows.

AI interior design: upload a room photo, pick a style, palette and budget, and get a redesigned room with real catalog products you can buy. I rebuilt the Python/FastAPI generation backend around Gemini (retries, failure classification, image-quality gate with credit refunds, scored product retrieval) and built the Flutter app's client flows.

Production-style RAG service: hand-written chunking and BM25, pgvector hybrid search with RRF fusion and reranking, cited answers, multi-tenant access control, and a rag-eval CLI that measures recall@k, MRR and faithfulness and fails CI on quality regressions.

Agent backend with permissioned tool calling, human-in-the-loop approvals, taint-based prompt-injection defence, SSRF-safe tools, crash-safe durable runs and a 48-case agent evaluation suite.

OpenAI-compatible LLM gateway over OpenAI, Anthropic, Gemini and Ollama: routing and fallback, circuit breaker, exact and semantic caching, API keys, quotas, cost tracking and Prometheus/Grafana. An outage benchmark exposed an unenforced-timeout bug; after the fix, failed requests dropped to 0.

Multi-tenant booking SaaS backend: Postgres row-level security, exclusion constraints against double-booking, idempotency keys, transactional outbox, Celery workers, signed webhooks and OpenTelemetry. k6 load testing surfaced and fixed a booking deadlock and a rate-limit status bug.

Distributed job queue on Redis Streams with retries, dead-letter queue, heartbeats and fencing-token locks. Chaos-tested with repeated kill -9; the atomic run-once mode lost 0 side effects.

Flash-sale ticketing API on Java 25 and Spring Boot 4: virtual threads for blocking I/O, structured concurrency for parallel pricing/fraud/inventory checks, scoped values, built-in API versioning, HTTP service clients and Postgres SKIP LOCKED seat holds. k6 measured virtual threads at 3,369–3,826 req/s vs 1,928–1,958 for platform threads on a 100 ms blocking call (busy laptop, single runs).

B2B payment collections platform in Java 21 and Spring Boot 3: JWT security with refresh rotation, JPA/Flyway on PostgreSQL, Redis, Kafka via a transactional outbox with idempotent consumers, Resilience4j around the payment gateway, signed webhooks and a Next.js frontend. 60 Testcontainers-backed tests; k6 measured ~687 payments/s at p95 21 ms on a laptop.

Local-first LLM usage and cost tracker for OpenAI, Anthropic and Gemini: a Python SDK, CLI and dashboard with OpenTelemetry export.

Workshop management web platform for STEI — schedules, operations, and admin workflows delivered as client work while at Agribid.

Full-stack SDUI platform with a drag-and-drop layout builder so mobile UI can update without app-store releases. Versioned publishing with validation, snapshots, and rollback. Flutter SDK renders JSON layouts into 30+ dynamic components, with multi-tenant auth and API security.

Education CRM with face-recognition attendance. I built the NestJS/PostgreSQL backend (raw parameterised SQL, 15 hand-written migrations, multi-centre tenancy, JWT + role-based access, Redis OTP rate limiting), built the Flutter tablet app with on-device face recognition (TensorFlow + Google ML Kit, local vector database), Android kiosk mode and Hive caching, running at 4–5 institutes, and co-built the Next.js admin dashboard.

Additional production Flutter / web / NestJS builds shipped while at Agribid and earlier roles — client portals, ops tools, and internal products that are live for users but not publicly listed (NDA / private distribution). Architecture walkthroughs and screens available on request.