Backend Engineering Services - Fredrick Nyang'au

Tagline: Backend systems for real business problems.

I design and build backend systems, REST APIs, and payment integrations using Python, FastAPI, and PostgreSQL. Focused on clean schema boundaries, deterministic data flow, and practical problem-solving for businesses and technical teams in Kenya and East Africa.

What I Help With

• Backend & API Development: Modular FastAPI backends, PostgreSQL 16 schema design, raw SQL via asyncpg, numbered migrations, and Pydantic validation.
• M-Pesa / Daraja Integrations: STK Push, C2B webhooks, storage-layer idempotency via UNIQUE constraints, and background worker queues.
• Backend Fixes & Improvements: Query optimization with CTEs, eliminating race conditions, and hardening multi-tenant query isolation.

Problems I Help Solve

• Manual workflows running on spreadsheets and paper logs
• Payment reconciliation and delayed service activation
• External API integrations with structured error handling and timeouts
• Data and backend reliability enforced via PostgreSQL constraints
• Internal operational backends connecting business workflows

Relevant Engineering Work

Frixel Connect: WiFi & Fiber ISP Billing Platform

KukuFiti: Poultry Farm Management API

Frequently Asked Questions

What backend stack do you build production systems with?

Production systems are built with Python 3.12+, FastAPI, PostgreSQL 16 (raw SQL with CTEs via asyncpg), Redis for caching and locks, Celery with RabbitMQ for background workers, and Dockerized deployments on Linux.

How do you handle M-Pesa Daraja payment integration and reconciliation?

We implement storage-layer idempotency keys, explicit transaction state machines (Pending, Processing, Confirmed, Failed, Reversed), webhook signature validation, and asynchronous worker queues to eliminate duplicate callbacks and dropped payments.

Can you automate MikroTik router billing and bandwidth management?

Yes, we integrate RouterOS API with FastAPI and M-Pesa to automate hotspot voucher creation, active session tracking, and dynamic bandwidth queue assignment in a single reliable workflow.

How are project pricing and delivery structured?

Fixed-price milestone pricing for well-scoped projects (50% deposit before implementation begins, 50% upon verified delivery). Ongoing retainers and architecture reviews are billed on a structured monthly basis.

Do you work with remote engineering teams outside Kenya?

Yes, all systems are packaged in Docker and architected for standard cloud platforms (Linux VPS, Railway, Render) with full observability, structured logging, and typed interfaces.

How I Work

Discover → Scope → Build → Verify → Handover

Discuss a project: Contact Fredrick Nyang'au or return to portfolio home.