Jahangir Alam Nabin
Senior Software Engineer | .NET, Distributed Systems & Applied AI
I build backend platforms and AI systems that ship, from multi-tenant SaaS to a production-grade RAG chatbot for a global automotive client. I'm just as at home on IBM z/OS mainframes: JCL, CICS, REXX, and z/OS-to-cloud integration. Currently leading a 6-developer team at Brain Station 23, and shipping my own Android app, Family Nearby, on a Go backend.
Case studies
RAG Chatbot with MCP External Data Sources for a Global Automotive Client
A production-grade retrieval-augmented generation backend answering vehicle owner-manual questions: hybrid retrieval, four-layer caching, releases gated on measured quality SLOs, and an MCP connection to external data sources, built so web text can never pass as the approved manual.
Procedure answers: 2× faster (8.5 s → 3.9 s)
- Python
- FastAPI
- Qdrant
- MCP
- PostgreSQL
Event-Driven Content Platform for a Global Automotive Client
The platform behind the chatbot: a .NET 9 modular monolith of 11 services with transactional-outbox messaging into Kafka, an admin panel, and a mobile BFF, delivered under my team leadership.
Bounded services: 11
- .NET 9
- PostgreSQL 17
- Kafka
- MassTransit
- Keycloak
Driver App and Mobile BFF for a Global Automotive Client
The surface drivers actually hold: a Flutter companion app and its .NET mobile backend-for-frontend. It covers consent and GDPR erasure, moving every driver's data from devices to accounts, weather-based AI driving tips that never show an error, and a support handoff that carries the chat context.
BFF automated tests: 1,500+
- Flutter
- Dart
- .NET
- PostgreSQL
- Redis
Family Nearby: an Android Family-Location App on a Go Backend, Built Solo
My own product. A family location-sharing app shaped by 12,180 competitor reviews, with a Kotlin/Compose Android app, a single Go server with a live WebSocket map, and tag-to-production CI/CD with automatic rollback. Built with Claude Code and now in Google Play review.
Automated tests: 4,300+ (1,204 Go · 3,134 Kotlin)
- Go
- Kotlin
- Jetpack Compose
- PostgreSQL + TimescaleDB
- WebSocket
Airflow 3 + BigQuery Data Layer for a Property-Tech AI Tool
The data foundation for an AI tool that finds energy waste in buildings: self-hosted Airflow 3, a 65-way mapped backfill into BigQuery, idempotent MERGE loads, partition-pruned cost, and a CI gate so no DAG ever reaches the scheduler by hand.
Rows backfilled: 45,113 in 5 min
- Apache Airflow 3.3
- BigQuery
- Python 3.12
- Docker Compose
- GitHub Actions
Multi-Tenant Compliance SaaS at 400-Endpoint Scale
A vendor-risk and compliance platform: tenant isolation with EF Core global query filters, CQRS across 54 feature modules, multi-IdP SSO, and Stripe subscription billing.
REST endpoints: 413
- .NET 8
- Next.js 15
- React 19
- PostgreSQL
- EF Core
4.5 Years Evolving a Freight-Forwarding ERP
From feature developer to top individual contributor on a 12-project .NET solution: 25+ logistics and accounting integrations, the full rate-to-shipment lifecycle, and a live migration to .NET 10.
Commits over 4.5 years: 3,600+
- .NET 10
- Angular 13 → 20
- SQL Server
- Redis
- SignalR
A Desktop Product with Fail-Closed Licensing
BizXtract: a sole-authored cross-platform desktop app and its licensing platform: Ed25519-signed device-bound entitlements, offline grace, idempotent billing webhooks, and crash-safe local storage.
Entitlement TTL: 12-hour signed packages
- .NET 10
- Avalonia
- Node.js
- MongoDB
- Stripe
One CRM, Five Surfaces: a Political Campaign Platform
A Canadian political-campaign CRM (canvassing, predictive dialing, donations, surveys, and analytics) delivered across web, mobile, a Chrome extension, a Gmail add-on, and a member portal.
Commits on the main client: 821
- Angular
- Node.js
- AWS Cognito
- Stripe
- Leaflet
What clients say
“It was really a pleasure to work with Md. Jahangir, he was professional, sharp and very talented. I would recommand him.”
“He is new to Upwork But he really have the skills to tackle the solution of the problem. It was really nice working with him. He even stayed the almost whole night to complete the project. Really hard working and honest guy. 100% recommended to the community”
“Jahangir is an excellent developer and great to work with, if you're looking for a skilled developer with both front and back end skills I highly recommend working with him.”
“he was so accurate and fast . We agreed to work with him again for next one. nice guy”
“Nice work i am very happy with your work.”
“He is perfect for angular jobs thanks”
Quoted word for word from client reviews. +5 more 5-star reviews on Upwork →
Evidence
Verified numbers, not adjectives
- Team led day-to-day
- 6 developers: presales, estimation, releases
- Platforms architected
- 2: compliance SaaS & automotive AI
- Client contracts delivered
- 20 at 100% Job Success · Top Rated
- Chatbot finds the right manual section
- 96.9% → 100% of test questions
- Chatbot procedure answers
- 2× faster · 8.5 s → 3.9 s
- Chatbot external data
- Website crawl live on dev · MCP tool loop built
- Disambiguation win-rate
- 100% across 27 cases
- SLO release gates
- ≥70% answers · ≥80% citations · ≤2% errors
- REST endpoints across platforms
- 1,400+
- External integrations
- 25+ logistics & accounting partners
- One product, 4.5 years
- 3,600+ commits, top contributor
- Own product, solo, ~2 weeks
- Android + Go · 4,300+ tests · tag-to-prod CI/CD
How I run projects, beyond the code
Team leadership
I lead a 6-developer team at Brain Station 23: planning, reviews and releases. Earlier I guided 2 intern developers at Democratik.
11-service platform delivered under my leadership
Presales
Presales for enterprise .NET and AI engagements: solution outlines, effort estimates and proposals that turn briefs into funded projects.
Presales · requirement analysis · estimation · releases
Client-facing requirement analysis
Requirement sessions directly with clients; vague briefs broken into task-level scope everyone can agree on before work starts.
20 direct-client contracts · 100% Job Success
Architecture planning across projects
Architect of a multi-tenant compliance SaaS (CQRS, 54 modules) and an automotive AI platform, plus an 11-service modular monolith with Kafka outbox.
413 REST endpoints · MCP tool loop · 2× faster answers
Effort estimation
Line-by-line scope → per-task hour workbook the client can inspect → calendar-dated timeline → fixed quote tracked against the workbook.
Workbook-based quotes, progress reported against them
Project delivery
Releases gated on measured quality SLOs, 5 CI/CD pipelines, and a live migration of a 12-project ERP to .NET 10 without pausing delivery.
SLO gates: ≥70% answers · ≥80% citations · ≤2% errors
Mainframe & z/OS
IBM Cloud Wazi port
Ported and extended an open-source COBOL/CICS/DB2 airline system to a fresh z/OS 3.1 instance on IBM Cloud Wazi, from VPN networking to green screen, 30+ errors diagnosed. Demonstrated at a conference in Japan.
6 CICS + 3 batch programs · 10 DB2 tables
z/OS → cloud SFTP consulting
For a US mainframe software vendor: root-caused a JCL job that reported success while its BPXBATCH SFTP upload silently failed; shipped production JCL, a REXX generator, and runbooks.
4 defects from one JCL review
The toolbox
JCL, CICS, BMS, COBOL, DB2, REXX, BPXBATCH/USS, EBCDIC conversion, Zowe CLI, TN3270: modern engineering discipline applied to big iron.
Two written-up case studies
Experience
Senior Software Engineer · Brain Station 23 PLC, Dhaka
Jul 2025 – Present
- Lead a 6-developer team; presales, requirement analysis, effort estimation, releases.
- Architect a multi-tenant compliance SaaS and an automotive AI platform with a RAG chatbot.
Software Engineer (.NET & Angular) · SkyTech Solutions (Codezzi), Dhaka
Jan 2025 – Jul 2025
- CRM features in .NET Core and Angular; ChatGPT, Stripe, SES, and Google Ads integrations.
- WinForms + Selenium desktop data-collection product with licensing.
Software Engineer (.NET & Angular) · Freightoscope, FL, USA (Remote)
Jan 2022 – Present
Full-time to Feb 2025; part-time consulting since.
- Freight-forwarding ERP: 159 controllers, 1,000+ endpoints, 526 Angular components.
- 25+ integrations, rate lifecycle, Redis/SQL performance, 5 CI/CD pipelines.
Software Engineer (.NET, part-time) · Quadiro Technologies LLP (Remote)
Nov 2021 – Jun 2022
- Yodlee financial-data integration in a Clean Architecture/CQRS application.
- Repository/unit-of-work patterns with xUnit/NSubstitute API tests.
Full-Stack Developer (Node.js & Angular) · Democratik, Laval, Canada (Remote)
Dec 2020 – Jan 2022
- CRM and campaign features: forms, email builders, Leaflet maps, Pusher chat.
- Chrome extension and Gmail add-on; guided 2 intern developers.
Software Developer Intern (.NET) · Code Source, Dhaka
Sep 2020 – Dec 2020
- FarmNet agro-fintech platform in ASP.NET Core MVC, EF Core, SQL Server.
- Database design and responsive UI from Figma designs.
Skills
Languages
- C#
- Python
- TypeScript
- JavaScript
- Go
- Kotlin
- Dart
- SQL
Backend, Frontend & Mobile
- .NET 8/9/10
- ASP.NET Core
- FastAPI
- Node.js
- Go
- Angular
- React/Next.js
- Android (Jetpack Compose)
- Flutter
- SignalR
- WebSocket
- Protobuf
- REST APIs
- RxJS
- NgRx
AI & LLM Engineering
- RAG
- LLM integration
- Generative AI
- Prompt engineering
- LangChain
- Semantic Kernel
- MCP (Model Context Protocol)
- Tool calling / agent loops
- OpenAI, Anthropic, Gemini
- Cohere reranking
- Qdrant
- pgvector
- Hybrid search (BM25, RRF)
Architecture & Messaging
- Clean Architecture
- CQRS (MediatR)
- Modular monoliths
- Microservices
- Domain-Driven Design
- Kafka
- MassTransit
- Transactional outbox
- SOLID
Data & Cloud
- PostgreSQL
- SQL Server
- MongoDB
- Redis
- EF Core
- Dapper
- AWS (EC2, S3, ECS Fargate, RDS)
- Azure (Functions, Blob, DevOps)
- Docker
- GitHub Actions
- Cloudflare (DNS, R2, Pages)
- VPS + Caddy
- IBM Cloud
Quality & Security
- xUnit
- Testcontainers
- Architecture tests
- pytest
- SonarQube
- Serilog/Seq
- Prometheus
- Keycloak
- SSO/OIDC
- JWT
- RBAC
- GDPR consent & erasure
- Agile/Scrum
- AI-assisted engineering
Mainframe & z/OS
- IBM z/OS
- JCL
- CICS
- BMS
- COBOL
- DB2 for z/OS
- REXX
- BPXBATCH & USS
- SFTP (Co:Z, OpenSSH)
- Zowe CLI
- IBM Cloud Wazi
- EBCDIC conversion
- TN3270
Beyond the day job
- Independent freelance record: Top Rated, 100% Job Success across 20 contracts and 2,439 logged hours.
- Family Nearby: my own family location-sharing app: Android + Go, built solo with Claude Code, now in Google Play review.
- Ship complete products solo: a licensed cross-platform desktop app with fail-closed Ed25519 entitlements.
BSc in Computer Science and Engineering, American International University-Bangladesh · CGPA 3.91/4.00 · Magna Cum Laude · Dean's List · Mar 2020
English (fluent) · Bengali (native)