Srejon Khan

Architect enterprise-scale and electro-optical systems from scratch for large-enterprise and defense-sector clients. Lead requirements analysis on contracted projects, translating client and stakeholder needs into technical specifications and scoped deliverables. Present technical strategy and project direction to senior leadership in high-value client pitches.

Designed and built an internal envelope-encryption package (TypeScript) implementing MEK/KEK/DEK with key rotation. Replaced an earlier HashiCorp Vault (EaaS) dependency and reduced service startup time by 70% via transparent decryption. Contributed to PSD2-SCA compliant Payment System with automated SEPA flows and reconciliation with the goal of near-zero audit flags. Led a team of 6 engineers to develop an internal monorepo template adopted by all services, reducing new-project core feature bootstrapping. Engineering backend services for Psyscreen, a LiveKit/WebRTC video platform for clinical psychological screening. Automated project bootstrapping & incident runbooks, reducing 20 dev-hrs/mo and reducing mean recovery from avg 45 min to avg 10 min.

Built Ticketing Service (Node.js, MongoDB); Load-tested to sustain millions of emails/day at p95=150 ms, with auto-deduping projected to reduce SLA from 4 h to 1.5 h. Built privacy-compliant Medical API and Postgres backend (ISO/IEC 27001, BD Telemedicine 2020) for Hurtlebee-NICUSys, a NICU vitals dashboard for clinicians. Deployed an edge-rendered Results Portal on Cloudflare Workers for BAIUST. Load-tested at ~420 req/s with p95 = 79 ms, serving 2.2K users. Launched GoodWords, a word-puzzle mobile game (Unity, C#) with a GitHub Actions CI/CD pipeline enabling same-day store releases.

Shipped Unity/C# XR gameplay sustaining 60 FPS, architected Firebase-based Backend. Authored open-source Firebase REST Client still powering a mobile game with 5M+ downloads and ~30K MAU.

Prototyped 2 hyper-casual titles in 4 weeks. Built a music beat-sync level generator that designs a 60-sec level in < 0.5 sec, reducing designer effort by around 80%. Maintained internal code guidelines, driving zero regression bugs across all sprint releases.

Implemented gameplay functionalities (Unity, C#) for a PC Title and a Mobile Title, boosting average session length. Rapidly prototyped several gameplay functionalities from concept, accelerating creative testing. Maintained clean code & Git workflows, reducing code-review defects.

Architected and built ArektaTransport, a full-stack Commuter and Fleet Management Platform for the Educational Institute or Public Transport Sector. Designed a cryptographic NFC Card protocol over MIFARE Classic 1K using HMAC-SHA256 to prevent Card Fraud and Cloning. Built a DRM License Platform (HMAC-structured keys, server-side activation, Hardware Fingerprinting, Complete Billing System per Org) protecting Arekta product lines. Built end-to-end live GPS Tracking (VTS) Pipeline: ESP32 + GPS + GSM firmware publishing over MQTT to EMQX Broker, consumed by Hono backend and broadcast via WebSocket to Web/Mobile Consumers.