Saidul Islam B.

13+Y | Senior Software Engineer | Enterprise, Public Software Services

Senior Software Engineer & Architect | 13+ Years | Top 1% Upwork | Expert Vetted 13+ years building backend systems and full-stack products for startups and enterprises. Top 1% Upwork freelancer, Expert Vetted. I solve complex technical challenges: $18M/year saved for Time Doctor, 8M+ users scaled at Zenius, 40+ provider integrations for Wego. I focus on scalable architecture, modern stack, and on-time delivery. What I bring to your project • Modern backend: Node.js/TypeScript, Nest.js, Go/Gin, Java/Spring Boot — microservice architecture, event-driven design, serverless (AWS Lambda, GCP), gRPC, message queues (NATS, Kafka, Redis Pub/Sub), parallel/concurrent processing. • Scalable data: PostgreSQL, MongoDB, Elasticsearch, Redis; ETL, time-series, analytics; database tuning, sharding, caching, parallel queries. • Cloud & DevOps: AWS, GCP, Digital Ocean; Docker, Kubernetes, Terraform; CI/CD; monitoring (Datadog, Sentry). • AI & automation: LLM integrations (OpenRouter), AI-assisted tooling (Cursor, CodeRabbit), custom AI agents and RAGs, workflow automation (n8n), ML/TensorFlow, voice-driven systems (Google AI Services). • Frontend: React, Angular, Vue; TypeScript, Redux, real-time (WebSockets, SocketIO, SSE); responsive and PWA-ready UIs. • Payments & integrations: Payment gateways (Stripe, Paddle, MangoPay, Upvest), third-party APIs, webhooks, and secure auth (OAuth2, JWT). • Multi-tenant & complex B2B systems: Tenant isolation, row-level security, RBAC, and strict data segregation per tenant; designed and delivered multi-tenant platforms (e.g. ticketing, fleet/ops, SaaS) with role-based access, real-time sync, and per-tenant visibility, so different orgs or depots get the right data and permissions. • Enterprise & compliance: GDPR, HIPAA, SOC 2, ISO 27001; enterprise security, encryption, audit trails, multi-region deployments. • Leadership & project management: Leading teams, converting business to technical requirements, architecture decisions, code reviews, agile methodologies, technical documentation. Proven outcomes • Time Doctor (USA): Legacy payment migration to Paddle; Nest.js microservices, GCP, Pub/Sub; $18M/year saved, 9-month delivery, 24/7 monitoring. • Zenius (Indonesia): LMS and infra for 8M+ users; Kafka, GraphQL, Neo4j, sharding and caching; new revenue stream (Zencore). • Wego (Dubai/Malaysia): Hotel metasearch; 40+ providers, ETL, WebSockets, gRPC, NATS; real-time pricing and search. • Exporo (Germany): Fiat + crypto payment; FSM (XState), RxJS, AWS serverless. • BRTC (Bangladesh): Multi-tenant ticketing; Nest.js, React admin, Android POS, real-time sync. • Accordium (Malaysia/Denmark): First SaaS version; React, Java/Spring Boot, CQRS; helped secure Series B funding. • Movingwalls (Malaysia): First DOOH booking platform; IoT data pipeline, real-time analytics, D3.js. • BigWIFI (Canada): Customer engagement platform; Nest.js, real-time diagnostics, live IT support marketplace. • Suprema/Biostar 2 (South Korea): Performance optimization; 1TB+ time-series data migration, Node.js refactoring, Karate test automation. • CapitakDK (Malaysia): Voice-driven AI system for Oil & Gas; Google AI Services, ML, GraphQL. I focus on clean architecture, event-driven and microservice patterns, and production-grade observability. I’ve led and mentored engineers, written technical docs, and delivered for clients in the USA, Europe, and Asia. Delivering on time and leaving a maintainable codebase is how I work. Why clients choose me • Results-driven: I focus on outcomes, not just code. Every project delivers measurable business impact. • On-time delivery: I've never missed a deadline. I communicate clearly, set expectations, and deliver what I promise. • Clean code: I write maintainable, well-documented code following best practices. Your team can take over seamlessly. • Scalable architecture: I design systems that grow with your business. Microservices, event-driven patterns, proper database design. • Full ownership: I handle backend, integrations, infrastructure, and documentation. I mentor teams and write technical docs. • Global experience: Worked with clients across USA, Europe, and Asia. Comfortable with remote collaboration and different time zones. Tech snapshot Languages: TypeScript/JavaScript, Go, Java, Python, PHP | Backend: Nest.js, Express, Spring Boot, Gin | GraphQL, REST, gRPC Data: PostgreSQL, MongoDB, Elasticsearch, Redis, Neo4j, DynamoDB | Cloud: AWS, GCP, Digital Ocean DevOps: Docker, Kubernetes, Terraform, CI/CD, Datadog | Real-time: WebSockets, SocketIO, SSE, MQTT AI/ML: OpenRouter, Cursor, CodeRabbit, custom AI agents, RAGs, n8n, TensorFlow | Architecture: DrawIO, Lucidchart, PlantUML, Mermaid, C4 Model Project Management: Jira, Trello, Asana, Linear, Notion | Other: Kong, OAuth2, JWT, IoT, blockchain, React Native Let’s build something that scales and ships.