Integration · REST · gRPC · Payments
APIs & Payment Gateways
Getting two systems to talk when one of them does not want to. The job nobody wants — and the one I enjoy.
The problem is never the happy path
Integrations work fine in testing. The trouble starts when the provider responds differently from its documentation, when a call times out after the charge already went through, when a webhook arrives twice, or out of order. Serious integration is about what happens when things go wrong — because they will.
What is included
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Charges that never duplicate
An idempotency key on every operation. A provider retry never becomes a second charge on the customer’s card.
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Reliable webhooks
Receiving, signature validation, tolerance to repeated and out-of-order delivery, and a queue to reprocess failures.
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Reconciliation
What the gateway says happened matches what your system recorded. When it does not, the report shows it.
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Retries with judgment
Not every failure should be retried. Network errors yes; a bank decline no. The difference prevents wrongful charges.
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Your own REST and gRPC APIs
When you are the one who needs to expose data. Versioning, authentication, rate limiting and documentation.
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ERP and legacy connections
Including old systems that only talk through files or databases. I have seen it all.
Why work with me
I work with withdrawal and deposit APIs, payment gateways, split payments, invoicing and identity verification in systems where the money is real. Idempotency, audit logs and partial-failure handling are not decoration in this context — they are what prevents losses.
Frequently asked questions
Which gateway do you work with?
Whichever makes sense for your case. I have integrated many and the pattern is similar; what changes is the documentation and each one’s quirks.
What if the provider has poor documentation?
It happens a lot. The way through is testing against the sandbox and mapping the real behavior, which sometimes differs from the docs.
Can you integrate an old system with no API?
Almost always. Database, files, automated email or even the UI — there is a way. Some are ugly, but they work and are honest about the maintenance cost.
Who handles it when the provider changes its API?
If there is a maintenance contract, me. Otherwise, I deliver it documented so your team can adjust it.
Tell me what you need
A two-minute brief. I reply within one business day — personally.