Md. Jahangir A.

Need a backend, full-stack, or AI system that holds up in production, not just on a demo branch? That's what I do. I'm a senior software engineer with 6+ years building web apps, desktop products, data platforms, and enterprise integrations for clients in the US, Canada, and Europe. Clients usually come to me with one of these problems: - "Our API is slow or falls over under load." I profile it, fix the queries and caching, and add retries, idempotency, and monitoring so failures stop reaching your users. - "We need a real product, not a prototype." Secure auth, roles and permissions, billing, background jobs, licensing, automated tests, and CI/CD are part of the build, not a phase two. - "We want AI over our own documents but it keeps answering wrong." I build RAG pipelines with hybrid search, reranking, and measured retrieval quality so answers are traceable. - "Our legacy mainframe code needs to run somewhere modern." I deploy and repair COBOL/CICS/DB2/JCL systems on z/OS and IBM Cloud. WHAT I WORK WITH Backend: .NET Core, Python, FastAPI, Node.js, REST APIs, Clean Architecture, CQRS, Kafka, MassTransit, SignalR, Hangfire Frontend: Angular, React, Next.js, TypeScript, RxJS, NgRx, Tailwind, Material UI Data: PostgreSQL, SQL Server, MongoDB, Redis, Qdrant, pgvector AI: RAG, LangChain, OpenAI, Cohere, hybrid vector + BM25 search, reranking, evaluation Cloud and DevOps: AWS, Azure, IBM Cloud, Docker, GitHub Actions, Azure DevOps, xUnit, pytest Mainframe: z/OS, COBOL, CICS, DB2, VSAM, JCL WHAT I'VE DELIVERED - A multi-tenant vendor risk platform covering supplier onboarding through audits and remediation, with enterprise SSO, granular permissions, Stripe billing, and AWS deployment. - Three years on a freight-forwarding ERP: 1,000+ endpoints, 25+ carrier and accounting integrations, and the full rate-to-shipment lifecycle. - A licensed Windows and macOS desktop product with signed entitlements, offline grace periods, and crash-recovery testing. - A multilingual vehicle-manual chatbot with intent classification and an automated retrieval-evaluation harness. - Technical leadership of a 6-developer team across architecture, estimation, and releases. HOW I WORK I plan carefully before writing code, clarify anything that is unclear, and provide an honest estimate before development begins. I will also tell you early if an approach is risky or unlikely to work. You will receive working increments that you can review throughout the project - not a month of silence followed by unexpected results. I always take ownership of project and meet the deadline I commit to. I have maintained a 100% Job Success Score and delivered more than 2,400 hours of work on Upwork. Some of my project details are in my portfolio and work history below. Send me your requirements, and I will reply with a clear technical approach, the main trade-offs, and a realistic delivery timeline.