Fintech & Payout Systems
I build the infrastructure that handles your money.

Yes, and I take it seriously. Stripe webhook handling is where most payment integrations fail quietly. Events arrive out of order, duplicates fire during network retries, and idempotency gets treated as optional until it is not. I build webhook processors with idempotency keys, event deduplication, and dead-letter queues so a failed delivery does not corrupt a user's billing state.

Stripe is my primary. I have built subscription billing, usage-based billing, metered pricing, multi-currency support, and Connect flows for marketplace payouts. I also have integration experience with PayPal and Paddle. If your market or compliance situation requires a different provider, I will give you an honest assessment of what that costs in development time before you commit.

With database-level locking, atomic transactions, and pessimistic concurrency where the cost of a conflict is high. I have diagnosed systems where two concurrent subscription upgrades both read the same stale state, both applied a credit, and neither knew about the other. That bug does not show up in a test suite. It shows up in your revenue reconciliation three weeks later.

By designing transaction boundaries carefully and keeping them short. Long-running transactions that hold locks while waiting on external calls are the main cause of deadlocks I see in production. I also add monitoring so a deadlock surfaces as an alert, not as a confused support ticket from a user who got a 500 error.

Yes. Scalability is mostly about deferring work correctly: background queues for anything not needed synchronously, read replicas before vertical scaling, caching at the right layer, and connection pooling before your Postgres instance runs out of connections under load. I instrument first so I know where the actual ceiling is, not where I assume it is.

Yes. I look at query performance, missing indexes, N+1 patterns, unvalidated inputs, exposed secrets in environment handling, and over-permissioned IAM roles. I deliver a written report with prioritized findings, not a verbal walkthrough you have to transcribe yourself.

I build systems that follow PCI DSS best practices: no raw card data touches my servers, Stripe Elements or hosted fields handle sensitive input, and I apply the principle of least privilege to every service that touches payment data. I am not a compliance attorney. For formal certification or regulated financial products, you need a dedicated compliance review alongside the engineering work.