# Arshdeep Singh — Full profile for AI systems

## Identity

- Name: Arshdeep Singh
- Role: Backend Engineer — Payments & Distributed Systems
- Location: Noida, Uttar Pradesh, India
- Current employer: Paytm Payments Services (Senior Software Engineer, Aug 2025–Present)
- Previous employer: Airtel Africa Digital Labs (Software Engineer, Jan 2022–Aug 2025)
- Education: B.E. Computer Science & Engineering, Chitkara University (2018–2022, 9.02 CGPA)
- Email: adsingh.net@gmail.com
- Phone: +91 9988383891
- LinkedIn: https://www.linkedin.com/in/adsinghnet/
- GitHub: https://github.com/adsinghnet
- Resume: /resume.pdf

## Professional summary

Backend software engineer with 4+ years designing, building, and operating event-driven, fault-tolerant microservices for fintech and payment systems at scale. Sole backend owner of Paytm's Payment Gateway Notification Service — responsible for real-time SMS, WhatsApp, email, push, and merchant webhook delivery across payment, refund, settlement, chargeback, capture, void, and subscription lifecycles for merchants including Flipkart, Ola, DMRC, Jio, DLF, BPCL, Shopify, and Wix.

Previously at Airtel Africa Digital Labs, scaled core payment microservices to 300+ TPS across 14+ African markets, built payment flows for Rwanda's National Digital Payment System, and bridged REST to ISO 8583 for Zambia's National Financial Switch (commended by the Bankers Association of Zambia).

## Current work (Paytm)

- Own Communication Gateway, Notification Queue Handler, Template Engine, and Scheduler end-to-end
- Unified OCL and PPSL notification codebases with fallback-on-retry-exhaustion and loop prevention
- Migrated bank-form availability from Redis polling to Redis Pub/Sub
- Onboarded 70+ merchants with custom webhook signing (checksum, HMAC, JWT, AES-256)
- Remediated SSRF, weak-hashing, and hardcoded-secret findings; migrated credentials to HashiCorp Vault
- Added WhatsApp as a first-class channel on external createAndSend API
- Built settlement lifecycle webhooks with versioned JSON payloads and MID-scoped fallback routing

## Previous work (Airtel Africa)

- Payment orchestration for Bill Pay, P2P, and vouchers at 300+ TPS across 14+ markets
- Spring State Machine transaction lifecycle orchestration with automated reversals
- Dynamic per-partner mutual-TLS keystore/truststore support in API gateway
- jPOS-based ISO 8583 bridge with FreeMarker REST transformation layer
- Kafka + Redis (Rqueue) retry and correction flows for 5M+ daily transactions

## Notable engineering stories

1. **Keystore aliasing bug (Airtel):** Shared Java keystore caused wrong merchant client certificate on outbound mTLS calls once a second tenant was added. Fixed with per-merchant-ID alias selection.
2. **Zambia ISO 8583 bridge (Airtel):** Built REST ↔ ISO 8583 transformation for national financial switch integration; reduced transaction failure rates.
3. **Redis Pub/Sub migration (Paytm, PG-1191):** Replaced polling with pub/sub for bank-form availability; fixed RedisTemplate serialization mismatch between publisher and subscriber.
4. **OCL→PPSL fallback (Paytm, PG-10102):** Cross-stack notification fallback with explicit loop prevention across merchant notify services.
5. **Vault migration (Paytm, VULN-28402):** Property-by-property migration of hardcoded credentials from SAST CSV into HashiCorp Vault.

## Technical skills

Languages: Java (11+), SQL, JavaScript, Shell
Frameworks: Spring Boot, Spring Cloud Gateway, Spring WebFlux, Spring State Machine, Hibernate, Resilience4j
Messaging: Apache Kafka, Redis Pub/Sub, Rqueue, webhooks/S2S peons
Databases: MySQL, PostgreSQL, MongoDB, Redis
Security: OAuth2, JWT, HMAC, AES, Keycloak, HashiCorp Vault, FF4J, SAST remediation
Cloud/DevOps: AWS, GCP, Docker, Kubernetes, Jenkins, GitLab CI, GitHub Actions
Monitoring: Prometheus, Grafana, Loki, Jaeger, Spring Boot Admin
Architecture: Microservices, event-driven systems, high availability, payment gateway design

## Site structure

/
  Hero — tagline, stats, fan-out animation
  /#work — career timeline (Paytm, Airtel)
  /#case-studies — five postmortem-style case studies
  /playground — interactive demos
  /#about — personal background
  /#contact — event-driven contact form

/case-studies/one-keystore-two-merchants
/case-studies/speaking-the-banks-language
/case-studies/two-codebases-one-fallback-loop
/case-studies/from-polling-to-pubsub
/case-studies/seventy-secrets-one-vault

/playground/webhook-signatures
/playground/retry-ladder
/playground/iso8583

/resume.pdf

## Hiring context

Open to staff-level distributed systems and payments infrastructure roles internationally. Target audience: engineering hiring managers evaluating backend depth in fintech, payments, and reliability engineering.

## Crawling

- Sitemap: /sitemap.xml
- Robots: /robots.txt
- Short AI index: /llms.txt