Jahangir Nabin

Projects

Deep dives with architecture and measured results, including two IBM z/OS engagements, plus smaller work worth a mention.

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

Porting a COBOL/CICS/DB2 Airline System to IBM Cloud Wazi

An open-source COBOL airline management system taken from a Git clone to a fully working online + batch application on a fresh IBM z/OS 3.1 instance on IBM Cloud Wazi: 30+ deployment errors diagnosed across 11 phases, from VPN networking to CICS pseudo-conversational bugs. Demonstrated at a conference in Japan.

Errors diagnosed: 30+ across 11 phases

  • IBM z/OS 3.1
  • IBM Cloud Wazi
  • CICS TS 6.2
  • DB2 v13
  • Enterprise COBOL 6.5

Root-Causing a Silent z/OS-to-Cloud SFTP Failure

Consulting for a US mainframe software vendor whose JCL job reported success while its BPXBATCH SFTP upload silently died. Decoded the masked exit codes, found four defects in a single JCL review, and delivered production JCL, a REXX command generator, and runbooks for two SFTP stacks.

Defects found: 4 from one JCL review

  • IBM z/OS
  • JCL
  • BPXBATCH
  • REXX
  • SFTP

More work