# Mustafa Shaikh — Senior Backend Engineer

> "I build backend systems that stay correct when the network doesn't."

Mustafa Shaikh is a Senior Backend Engineer based in Islamabad, Pakistan (remote-first, open to relocation) specializing in distributed systems, event-driven architectures, offline-first data synchronization, relational integrity, and failure recovery.

## Contact & Links
- Website: https://shaikhmustafa.dev/
- Email: mustafajahangirshaikh@gmail.com
- LinkedIn: https://www.linkedin.com/in/shaikhmustafa
- GitHub: https://github.com/mustafa-shaikh
- Résumé: https://shaikhmustafa.dev/resume/Mustafa_Shaikh_Senior_Backend_Engineer.pdf

## Core Technical Competencies
- Distributed Systems & Messaging: BullMQ, Redis Pub/Sub, Apache Kafka, NATS, AWS SQS, AWS IoT Core, Server-Sent Events (SSE), WebSockets.
- At-Least-Once Delivery & Resilience: Idempotency keys, device-side ACK contracts, exponential backoff, dead-letter queues, disaster recovery state snapshots.
- Offline-First Architecture: Local queues, schema-per-tenant isolation, conflict-safe reconciliation, tombstone records, multi-locale / multi-currency offline POS engines.
- Data Integrity & Relational Modeling: PostgreSQL, DynamoDB, MySQL, Amazon RDS, transaction chunking, write-consistency under peak load, financial reconciliation.
- Polyglot Backend Languages: TypeScript/Node.js, Java (Spring Boot), Go, Python.

## Flagship Systems & Case Studies
1. NoreOS (https://shaikhmustafa.dev/work/noreos/):
   - Solo-architected offline-first retail operating system designed so retail stores never lose a transaction when connectivity drops.
   - Strict schema-per-tenant PostgreSQL isolation, 10 script-correct locales, multi-currency.
   - Tested under an 80% coverage gate with 287 Flutter + 248 React unit/widget tests and 396 end-to-end API flows. Built using agentic engineering workflows. Live at https://noreos.com/.

2. AIO Restaurant Platform (https://shaikhmustafa.dev/work/aio/):
   - Real-time kitchen order delivery serving ~500 production devices with at-least-once delivery (BullMQ, Redis Pub/Sub, SSE, device ACK) and 6-hour exponential-backoff auto-recovery.
   - Load-tested to 10,000 concurrent connections.
   - Unified device-status heartbeat pipeline across 4 fragmented stores into AWS IoT Core -> SQS -> Redis with DynamoDB DR snapshots.
   - Rewrote gift card service in ~10 days; corrected POS payment rounding and cash drawer reconciliation tolerances.

3. Fintech & B2B Platforms (https://shaikhmustafa.dev/work/fintech/):
   - Small World Financial Services: Monolith-to-microservices migration, centralized multi-variant i18n translation service, 8-engineer code review framework.
   - Dastgyr Technologies: Payment & dispute management, serverless PII chat masking, nested surveys portal for BI.

## Technical Writing
- At-least-once delivery is easy; exactly-once is a product decision (https://shaikhmustafa.dev/writing/at-least-once/)
- Offline-first is a data-model problem, not a sync button (https://shaikhmustafa.dev/writing/offline-first/)
- Designing for the six-hour outage (https://shaikhmustafa.dev/writing/six-hour-outage/)