Lavish Kumar

Payment systems · technical leadership · consulting

Payments architect and consultant for reliable money movement.

I design and review card-present, UPI, and payment-integration systems. Eight years across Verifone, Juspay, and PayPal.

Request an architecture review ↗See selected work ↓
8 years in payments3 payment companies200+ people mentored

Core expertise

Card-present payments, compliance, and reliability.

authorize→settle→reconcile

EMV, P2PE, ISO 8583, terminal integrations, idempotency, and refunds.

Selected work

Payment systems I have worked on.

Sanitized accounts of real engineering work. Each one focuses on the problem, the decisions, and the result.

01Card-present payments

Making a terminal-partner integration production-ready

Connected a terminal-partner path to an in-store payments platform while keeping APIs, certification, and testing aligned.

  • Cross-team integration planning
  • EMV L3 certification support
  • Transaction and reader API design
  • Partner testing unblockers
Card-presentEMV L3GraphQLPartner integrations
Read case study ↗
02Payment reliability

Designing recovery for the payment unhappy path

Designed recovery paths for timeouts, reversals, voids, and refunds so retries do not create duplicate money movement.

  • Idempotency-key transaction lookup
  • Reverse-transaction API design
  • Queued refund handling
  • Merchant-facing API contracts
ReliabilityIdempotencyRefundsAPI design
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03UPI infrastructure

One UPI service interface across different clouds

Built UPI capabilities across cloud and bank-managed deployments without turning each environment into a separate product.

  • UPI Number Mapper
  • DynamoDB and PostgreSQL interface
  • Distributed cache design
  • NPCI certification coordination
UPIRustAWSGCP
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How I help

Clarity when the payment system is hard to ship.

Useful when a team is facing certification, integration, reliability, or delivery risk.

01

Payment-flow review

Trace authorization, routing, retries, idempotency, webhooks, refunds, and reconciliation before they become production incidents.

02

Integration architecture

Define provider and terminal boundaries, transaction states, API contracts, and a practical delivery sequence for end-to-end payment solutions.

03

Certification and delivery readiness

Prepare EMV L3 and P2PE-related engineering work, partner testing, technical documentation, and cross-team execution.

A focused architecture review.

I trace the flow, provider boundaries, transaction states, failure handling, and delivery risks. You leave with decisions and a practical next step.

Discuss a system ↓

About Lavish Kumar

Eight years across card-present, UPI, and payment infrastructure.

I am a tech lead for the card-present team at PayPal, coordinating across India and the US. Before that, I worked on UPI payment services at Juspay, and card-reader software and a high-volume payment switch at Verifone.

My core area is card-present payment processing: EMV flows, P2PE boundaries, ISO 8583 systems, terminal integrations, and the APIs around them. I have led multiple teams, evaluated Staff candidates, participated in hiring cycles, and mentored more than 200 people.

Card-present · EMV · P2PE · ISO 8583UPI · NPCI · payment railsRust · Java · C++ · RubyAWS · GCP · GraphQL · SQL

Start a conversation

Tell me where the payment flow breaks.

Describe the system, the constraint, or the failure mode. I'll reply with whether I can help and what a useful first step looks like.