Backend systems that
hold under load
I'm Sabbir Mahmud — a full-stack engineer working on distributed backends, real-time pipelines, and the infrastructure underneath them. Django and Node on the server, React and Next on the surface.
Where I've been building
Four years across education platforms, restaurant operations, and media pipelines — each one a system that had to stay up while it grew.
Full-Stack Engineer (Next.js / TypeScript)
- Architected a multi-repo educational platform composed of Next.js 16 (App Router) client portals, Next.js administrative dashboards, an Expo-powered React Native mobile application (Expo Router & Reanimated), and a Node.js/TypeScript Express API backend.
- Designed and implemented a scalable database schema using MongoDB and Mongoose ODM, integrating Connect-Mongo session storage, JWT auth security, and custom middleware handlers.
- Engineered a high-throughput question engine on the mobile app leveraging Shopify Flash-List for virtualized list performance and MathJax/WebView wrappers to dynamically typeset complex math equations.
- Developed a modular, multi-step exam builder using React Hook Form, Redux Toolkit, and Radix UI dialogs, supported by a backend compilation pipeline utilizing PDFKit and Puppeteer to generate high-fidelity PDF exam prints.
- Integrated Jodit React WYSIWYG editors and KaTeX math typesetting inside the moderator dashboards, enabling administrators to easily draft, categorize, and audit curriculum-aligned question sheets.
Backend Developer (Python, Django)
- Integrated the Otter API aggregation gateway with custom Django polling and webhook systems to sync real-time restaurant orders across multiple providers, enabling 35% client expansion.
- Implemented real-time bi-directional menu tracking and push notifications using Django Channels, WebSockets, and Redis Pub/Sub, boosting customer retention by 30%.
- Built a synchronization connector between Clover POS OAuth2 APIs and the local SQL database schema to automate ledger auditing and streamline cash management, reducing revenue leakage by 10%.
- Optimized background worker pipelines and scheduled tasks using Celery, Redis queue limits, and PostgreSQL query optimization, cutting server overhead by 5%.
- Developed reactive delivery dispatch maps using React/Redux, Google Maps, and Mapbox APIs with live coordinate interpolation, reducing routing overhead by 10%.
Full Stack Web Developer (Python || JavaScript)
- Architected a secure real-time bidding auction system using Ethereum smart contracts (Web3.js) and Next.js SSR to ensure immutable transaction logs, driving 50% of annual corporate revenue.
- Integrated global payment flows using Razorpay Webhooks, Stripe Elements, and PCI-compliant Express backend APIs to manage recursive SaaS subscriptions.
- Engineered multi-threaded Python Celery workers and async Node.js middleware to handle heavy file operations without blocking the event loop, boosting throughput by 35%.
- Designed an automated translator dispatch algorithm and a collaborative React vetting dashboard with atomic state management (Redux), boosting translation vetting accuracy by 20%.
- Orchestrated cloud pipeline workflows with speech-to-text (Whisper/Azure), neural translation, and text-to-speech APIs from AWS Polly and Google Cloud to automate video dubbing across 114 languages.
Things I've built and shipped
Open-source libraries, developer tooling, and production systems — each solving a problem I hit often enough to make it reusable.
Black AI IDE
A custom, telemetry-free distribution of VS Code featuring a built-in AI coding assistant and agentic loop engine, optimized for secure and private offline development workflows.
- Built-in AI coding assistant and agentic loop engine living in the activity bar
- 100% telemetry-free by default with all tracking endpoints completely patched out
- Security-hardened build with command filter capabilities and custom branding
- Automated cross-platform build pipeline (macOS, Linux, Windows) using VSCodium build system
BDPayments
A centralized payment gateway abstraction layer for Stripe, SSLCommerz, bKash, and Nagad. It offers a single, unified API interface for charge, refund, and retrieve operations across multiple providers with lazy-loaded adapters.
- Unified API wrapper for Stripe, SSLCommerz, bKash, and Nagad payments
- Dynamic runtime provider resolution via lazy-loaded adapters
- Normalized schema maps for charges, refunds, and query lookups
BDDeliveries
A centralized delivery gateway abstraction wrapper for Bangladeshi couriers including Pathao, Steadfast, and Paperfly. It provides a unified API for order creation, tracking, and cancellations with dynamic runtime loading.
- Centralized courier gateway for Pathao, Steadfast, and Paperfly APIs
- Automated parcel creation, real-time tracking, and package cancellation
- Dynamic load triggers for shipping carriers minimizing bootstrap weight
Express Controller Sets
Designed for Node.js/Express.js developers to minimize boilerplate route controls. Create a schema model, instantiate the controller set, and link routes. Supports validation via Mongoose, express-controller-sets-router, and S3 file uploading.
- Route control generation directly mapped from Mongoose schema configurations
- Built-in validation checks, request sanitization, and express-router bindings
- Integrated AWS S3 file uploading handling and local temp write cleanup
Python Advanced Invoice Generator
Automated document utility designed to compile high-fidelity PDF invoices. Renders dynamic schema data using Jinja2 templates into HTML, compiled into target PDF prints via Pdfkit and the wkhtmltopdf compilation engine.
- Automated dynamic PDF compilation using Jinja2 HTML templates
- Headless rendering via wkhtmltopdf binaries and Django environment bindings
- High-fidelity layouts accommodating multi-currency and detailed ledger listings
ISP Billing System
An enterprise billing and management automation system for Internet Service Providers. Integrates with Mikrotik API for bandwidth and radius profiles control, coupled with PayPal, Stripe, and SSLCommerz payment gateways. Manages invoice triggers, automated ledger entries, and features a collaborative user client portal.
- Mikrotik Radius Server Profile Integration
- Automated payment billing & gateway reconciliation
- Real-time bandwidth usage & connection tracking logs
What I reach for, and why
Grouped by the layer it operates at. The bar is honest — it reflects how much production time I've actually put behind each one.
Languages
Day-to-day, in production
Async services, Celery pipelines, scripting
Type-safe client and server business logic
The runtime underneath all of it
Backend
Where most of my time goes
DRF, Channels, ORM tuning, auth
Event-driven APIs, non-blocking workers
High-throughput async REST surfaces
Routing, middleware, request pipelines
Frontend
Interfaces over those systems
Component state, data flow, virtualization
App Router, RSC, SSR and caching
Expo Router, Reanimated, FlashList
Data
Schema design and query cost
Indexing, partitioning, transaction control
Document modelling, Mongoose ODM
Pub/Sub, queues, cache invalidation
Infrastructure
Getting it running and keeping it up
Containerized deploys, service isolation
Reverse proxy, load balancing, TLS
EC2, S3, VPC networking
Host configuration and shell automation
GitHub Actions, automated release pipelines
Let's build something that lasts.
Available for architecture consulting, contract engagements, and senior engineering roles. The fastest way to reach me is email.