Full-Stack Software Engineer
Janindu
Gayanga
Building scalable, real-time production systems across iGaming, Fintech & EdTech — currently building with AI & LLM APIs. 3 years+ delivering with Next.js, Node.js, Go & AWS.
Full-Stack Systems
End-to-end features from UI to cloud infrastructure
Real-Time Backends
WebSocket & Kafka pipelines for high-concurrency workloads
API & Microservices
Scalable REST / Go services with RBAC & OAuth 2.0
Cloud & DevOps
AWS deployments, Docker containerisation, CI/CD pipelines
About Me
Code built to
last
I'm Janindu Gayanga, a full-stack engineer with 3 years+ building production-grade systems — scalable REST APIs, microservices, and real-time WebSocket backends that handle real traffic.
At BotCalm, I ship across iGaming, Fintech, E-commerce & EdTech — with Next.js, Nest.js, Go & AWS in Agile teams. I've built payment gateway & crypto exchange integrations, and am actively building AI-integrated systems in my own time. Studied at SLTC Research University.
Expertise
Skills & Technologies
Frontend
Backend
Databases
Cloud & DevOps
Security & Auth
Also Working With
Career
Work Experience
From intern to software engineer — I've grown across iGaming, Fintech, E-commerce & EdTech, and am actively building AI-integrated systems. Always prioritising quality, performance, and continuous improvement.
B.Sc. (Hons) Software Engineering
Sri Lanka Technological Campus (SLTC)
2020 – 2024
July 2025 – Present
Software Engineer
BotCalm Private Limited · Sri Lanka
Architecting high-performance full-stack features with React / Next.js and Nest.js microservices on AWS. Building real-time iGaming & Fintech modules with WebSockets and Kafka for thousands of concurrent connections. Optimising cloud-native CI/CD pipelines and participating in rigorous Agile/Scrum code reviews.
August 2024 – June 2025
Associate Software Engineer
BotCalm Private Limited · Sri Lanka
Designed and deployed secure RESTful APIs and full-stack applications on AWS for four production projects across iGaming, Fintech, E-commerce, and Education. Integrated Crypto Exchange & Payment Gateway providers (Plaid, Coinbase Commerce), reducing per-integration time by 60%. Maintained high codebase integrity through structured code reviews.
March 2024 – November 2024
Software Engineer Intern
NEWNOP Private Limited · Sri Lanka
Delivered 5+ responsive web pages for the Lallaloi platform using Next.js and Tailwind CSS with AWS S3 asset management. Implemented systematic debugging protocols, contributing to a 30% reduction in reported UI defects.
March 2020 – March 2024
B.Sc. (Hons) Software Engineering
Sri Lanka Technological Campus (SLTC) · Padukka
Honours degree in Software Engineering. Award: CodeMania v2.0 (IEEE Computer Society SLTC) — Second Runners-Up. Coursera: Cloud Computing Applications (Cloud Systems and Infrastructure).
Portfolio
Featured Projects
Next.js · Nest.js · Go
Enterprise iGaming Platform
Real-time gaming platform serving thousands of simultaneous users with 90+ Lighthouse scores and 40% faster page loads. Full PWA with offline support and i18n (RTL). Event-driven microservices architecture with WebSocket & Kafka backends scaled to 10,000+ concurrent connections, sub-100ms latency. Hybrid MongoDB/PostgreSQL, RBAC, OAuth 2.0.
Next.js · Go · WebSockets
iGaming Platform — Admin Dashboard
Operations dashboard for the same ecosystem: live KPI charts monitored via Grafana, granular RBAC, and data-heavy tables handling 10,000+ records — built for real-time monitoring, alerting, and admin workflows.
Next.js · Nest.js · Microservices
Fintech Platform
Production-ready fintech platform featuring secure transaction flows, real-time payment processing, and a microservices backend. Containerised via Docker and deployed on AWS with full CI/CD. Built with Nest.js and Next.js with PostgreSQL for transactional integrity.
Nest.js · Go · PostgreSQL
Crypto Exchange & Payment Gateway
Unified backend service integrating 7 payment and crypto exchange providers including Plaid and Coinbase Commerce, reducing per-integration development time by 60%. Secure transaction flows with JWT & OAuth 2.0, containerised via Docker on AWS.
NestJS · Next.js 14 · PostgreSQL
AskLK — Bilingual AI Assistant
White-label RAG assistant any Sri Lankan organisation can point at its own documents — ask in Sinhala and get Sinhala, ask in English and get English, even when the source document is in the other language. Embeddings live in PostgreSQL via pgvector, so one SQL statement combines the tenant filter, document-status filter and vector search while staying transactionally consistent. Hybrid retrieval fuses vector and full-text results by Reciprocal Rank Fusion, and four anti-hallucination layers — a similarity floor that refuses before the model is ever called, prompt constraints, citation validation, and source cards rendered from retrieved rows — keep answers grounded. Ships with a 4.4KB gzipped Shadow DOM widget.
NestJS · Next.js 14 · PostgreSQL
QueueLK — Live Queue Management
Live queue display and phone page for Sri Lankan dispensaries, clinics and salons — patients scan a QR at the door, see how many are ahead of them, and get buzzed when they are two away, with no app to install. Token numbers stay gap-free and duplicate-free under concurrency through a row lock taken with SELECT FOR UPDATE, a UNIQUE constraint backstop, and a capacity check inside the same transaction. Idempotency keys written in that same transaction mean a double-tap on the staff tablet replays the first response instead of calling a second patient. Realtime via SSE over Redis pub/sub, in Sinhala, Tamil and English.
Next.js 14 · NestJS · Go
BookLK — Service Booking Marketplace
Open-source multi-vendor booking marketplace for Sri Lanka — customers book time slots with salons, clinics and repair services while vendors manage availability and payouts. Four-layer double-booking prevention (idempotency key, Redis SET NX lock, SELECT FOR UPDATE inside a Serializable transaction, and a UNIQUE constraint backstop) proven by a test firing 20 parallel bookings at a single slot. HMAC-SHA256 webhook verification against the raw body with an append-only money ledger, and refresh-token rotation with reuse detection. A Go service pushes live slot availability over WebSockets.
Go · Binance API · DeepSeek AI
AI Crypto Trading Bot
Autonomous 24/7 multi-coin trading bot for Binance Futures, written in Go. Ranks the market's top movers by 24h volume and volatility to rebuild its own watchlist every hour, then combines DeepSeek for trade decisions, Gemini for news sentiment, and Fibonacci / Elliott Wave indicators before entering a position. Risk controls cover position limits, stop conditions and profit-cycle resets; every trade is persisted to MongoDB so the bot learns from past losses, with Telegram alerts and a live web dashboard.
Next.js · Nest.js · PostgreSQL
School Management System
Comprehensive full-stack management system covering student records, staff management, timetabling, and academic tracking for a UK primary school. Deployed on AWS with PostgreSQL for reliable data flows and role-based access control.
Get In Touch
Let's Connect
Open to full-time roles, freelance projects, or conversations about building something great. I'd love to hear from you.