Bestine Payyappilly

Senior Frontend DeveloperMar 2024 – Present

• Owned mobile architecture, release engineering, and on-call as sole mobile architect for the iOS and Android apps, with 500k+ downloads.
• Designed and shipped custom Swift and Kotlin native modules for ECDH key exchange (prime256v1) and AES encryption, which moved card-transaction crypto on-device and out of the JS bundle.
• Hardened the apps against mobile threats with root and jailbreak detection, runtime protection, SSL pinning, biometric authentication, encrypted storage and payloads, and locked-down release builds.
• Delivered a Fixed Deposits product solo end to end and rebuilt the gold investment flow around pre-calculated return projections, so users can see the expected return before they invest.
• Cut hotfix turnaround with CodePush OTA updates checked on app resume, and automated Sentry source-map uploads so production crashes stay debuggable.
• Built reusable animation abstractions on Reanimated, Lottie, Rive, and Skia, so feature teams could ship consistent motion without touching native code.
• Led the student portal's React to Next.js migration on a documented runbook and rollback path, cutting page load time with no downtime at cutover.
• Designed the Postgres/Supabase schemas and server-side verification for 4 payment gateways. Every transaction is checked against the gateway instead of a client-side success callback.
• Built server-side attribution end to end: Meta CAPI on Django and GCP with cross-subdomain session stitching, plus a WebEngage migration onto CUID identity resolution while two brands merged.
• Built a RAG adaptive learning platform on pgvector and the Claude API, plus a LangGraph multi-agent pipeline for question-paper generation. A/B tested with 500 students, and 50 papers are in production.
• Mentored 4 engineers across mobile and web through code review, set the engineering standards both codebases follow, and partnered with founders on scope and prioritisation.

Frontend DeveloperFeb 2022 – Mar 2024

• Built the core prepaid-card and savings flows in React Native with Redux on Hermes. The state and navigation architecture from that work still runs the app.
• Handled the fintech lifecycle edge cases: re-authentication after backgrounding, force-update and maintenance gates, and deep links that survive PIN verification instead of being dropped.
• Built the web ecosystem from scratch: student, teacher, and admin portals plus two checkout surfaces. It now serves 500+ schools and 100,000 participants.
• Architected a Turborepo monorepo with 3 checkout apps on shared Razorpay, Stripe, and BillDesk infrastructure, so a gateway change shipped once instead of three times.