Abhishek Sharma
Staff Software Engineer at Visa, Bengaluru

I build payment systems that stay up.

10+ years building backend systems in Java across payments, e-commerce and logistics. Today I work on card payment authentication at 1,000 TPS and 99.999% availability.

Get in touch See my experience

Try it: authenticate a card payment

A simplified simulation of the public EMV 3-D Secure flow I work on. Timings are illustrative.

CheckoutMerchant
3DS ServerMerchant side
Directory ServerCard network
ACSCard issuer
  • Pick a risk level and run the payment to see each step.

About

  • Now: Staff Software Engineer, Visa Secure
  • Leading: a team of 4 engineers
  • Before: Porter, Jio Platforms, FirstHive, eMart
  • Based in: Bengaluru, India

I work on the Directory Server for Visa Secure, the part of EMV 3-D Secure that decides how a card payment gets authenticated before it is authorized. It's a system where a few minutes of downtime means real people can't pay, so most of my time goes into reliability, performance and making releases boring.

Before Visa, I scaled Porter's core services to handle 10x load, built fulfilment microservices and a Kafka retry library for Ajio at Jio Platforms, and ran a campaign engine and loyalty platform handling millions of requests at FirstHive.

I enjoy mentoring engineers through design and code reviews, and I'm always happy to talk about distributed systems, payments or growing into a Staff role.

Things I've built

Visa

Release automation for a payments platform

Releases on a 99.999% availability platform were slow and manual. I led a team of 4 to build an internal deployment tool that standardizes every release step and makes rollbacks predictable.

Release effort down 40%.

Porter

Scaling core services 10x

As part of the Tech Scalability pod, I profiled the hot paths, removed bottlenecks and partitioned large PostgreSQL tables that were slowing down critical queries.

10x load handled; query latency down 30%.

Jio Platforms

Kafka retry library

Async messages between fulfilment services were getting lost on transient failures. I introduced Kafka-based messaging and a reusable retry library with backoff and failure handling.

Adopted across 6 services; message reliability up 25%, downtime down 30%.

Side project

Distributed rate limiter on Redis

A token bucket rate limiter that keeps request counts consistent across many app instances by doing the check-and-decrement atomically in Redis. Try the idea below: the bucket holds 5 tokens and refills one per second.

Token bucket
Tokens available: 5 of 5

See my code on GitHub

Experience

    • Build the Directory Server for EMV 3-D Secure, which authenticates and authorizes card-not-present transactions between merchants and issuers.
    • Engineer a mission-critical platform processing 1,000 TPS at 99.999% availability on Java, Spring Boot, Kafka, Redis, gRPC and Kubernetes.
    • Lead a team of 4 engineers; built a deployment tool that cut release effort by 40%.
    • Scaled core backend services to handle 10x the previous load by finding and fixing system bottlenecks.
    • Implemented PostgreSQL table partitioning, cutting query latency by 30%.
    • Led 6 Spring Boot microservices for Ajio fulfilment across B2C, B2B and Grocery, improving shipment management efficiency by 35%.
    • Introduced Kafka and a retry library adopted across 6 services: 25% better message reliability, 30% less downtime.
    • Built the Label Service from scratch, cutting invoice and label processing time by 40%.
    • Raised pack service throughput by 50%; improved incident response time by 40% with centralized monitoring.
    • Star Performer FY 2023-24 (A* rating).
    • Led the campaign module of a customer data platform serving millions of requests; Java concurrency made campaign runs 30% faster.
    • Built WorldSwipe, a loyalty platform for high-volume points accrual and redemption.
    • Integrated payment gateways (Razorpay, Paytm, Stripe) and OAuth 2.0; cut API response times by 50% with Redis caching.
    • Built Java REST services for a CRM and client support-ticket platform on MySQL.
    • Optimized SQL queries for a 30% performance gain; set up JUnit testing and SonarQube.

Toolkit

Languages and frameworks

Java, Kotlin, Spring Boot, Hibernate/JPA, JUnit, Mockito

Distributed systems

Microservices, Kafka, event-driven design, REST, gRPC, caching, rate limiting, circuit breakers

Payments and security

EMV 3-D Secure, payment authentication and authorization, payment gateways, OAuth 2.0

Data

PostgreSQL, MySQL, Oracle, MongoDB, Redis, Elasticsearch

Cloud and delivery

AWS, Docker, Kubernetes, CI/CD, deployment automation

Observability

Prometheus, Grafana, ELK, Datadog

Let's talk

I'm happy to chat about Staff, Lead and Principal backend roles in payments and fintech, or about distributed systems in general.

Email abhishek.hcst15@gmail.com LinkedIn Profile GitHub abhishek-sharma-1993