Jul 2022 – Present · 3 yrs 8 mos · Noida, Uttar Pradesh, India · On-site

• 1. Worked across four production Android platforms: POS Terminal App, Driver Payments App, Customer Payments App, and RBE Enrollment App, delivering secure, high-scale fintech solutions on embedded POS hardware.
• 2. Architected a multi-mode card payment system (ICC, MAG, NFC) on PAX A910/A910S using Kotlin and PAX Neptune SDK, implementing concurrent card detection, EMV TLV parsing, and APDU handling. Supported 10,000+ fleet cards with ~99% read success and ~30% faster checkout.
• 3. Developed a BLE-based fuel pump controller using Bluetooth LE GATT, custom binary protocol, CRC validation, and foreground services, enabling wireless authorization across 50+ fuel stations with <2s preset latency and 95%+ connection stability.
• 4. Designed a secure POS terminal activation flow with RSA-2048 key exchange and automated TMK injection via PAX PED SDK, reducing onboarding time from ~30 minutes to <5 minutes across 1,000+ devices.
• 5. Built a PCI-DSS-compliant API security layer using AES-256, RSA, SHA-512, and custom OkHttp interceptors, securing 15K+ daily payment transactions with zero security incidents post-deployment.
• 6. Led fintech feature delivery across consumer and field apps by integrating Paytm, PayU, CCAvenue, and Juspay HyperSDK, processing ~100K monthly transactions, and building a real-time eKYC system supporting 50K+ enrollments/month with 95% first-attempt success.
• 7. Modularized offline NCMC transit payments into a dedicated module, migrated data to a purpose-built local database, and implemented a durable offline transaction backup layer to prevent fund loss beyond app lifecycle, including uninstall scenarios.
• 8. Built the Paytm Bus Transit POS app for high-throughput cashless ticketing in low-connectivity environments. Implemented wired/wireless ECR integrations, deep-link payment flows, and optimized networking using custom Retrofit TypeAdapters, reducing JSON parsing latency by ~80% on constrained POS devices.