Daniel Chen.

Payment gateway integration

A payment that works in the demo is easy. One that never double-charges, never loses a callback and reconciles at month end takes care. I have shipped payment integrations for a broker, a theme park and a payment provider.

What I can do

  • Payment gateway and PSP integration

    Checkout.com, Stripe, Octopus and other providers: payment sessions, 3-D Secure flows, webhooks and refunds.

  • Apple Pay and Google Pay

    Wallet payments as separate methods, tested end to end before release.

  • Webhook safety

    Signature verification before trusting a payload, idempotent processing, retries and alerts.

  • Reconciliation

    Status polling and reconciliation jobs, so a missed callback never turns into lost revenue.

  • Payment microservices

    A standalone, multi-tenant gateway with HMAC request signing, replay protection and key rotation.

Proof, not promises

How we would work

  1. 01

    A short call

    A no-obligation conversation about what you need, what exists already and what success looks like.

  2. 02

    A written scope

    What I will build, what I will not, the risks, and a fixed quote or a time-based estimate.

  3. 03

    Small, visible releases

    You see working software early and often, on a staging site you can click through.

  4. 04

    Handover and support

    Documentation, access and a clean handover, with ongoing support if you want it.

Questions

Which payment gateways have you worked with?
Checkout.com (cards, Apple Pay, Google Pay, Benefit), Stripe, Octopus in Hong Kong, and Malaysia's FIUU in sandbox. Most providers follow the same pattern, so a new one is mostly careful reading of their docs.
Some of our payments go missing or get credited twice. Can you fix that?
Usually it is a webhook that failed, arrived twice or was never verified. I trace the exact payment through your logs and the provider dashboard, then add idempotency and reconciliation so it cannot happen silently again.
Will you store card numbers?
No. Card data stays with the payment provider through hosted fields and tokens, which keeps your PCI scope small.

Tell me what you are building.

A few lines are enough: what it is, who it is for, and when you need it. The form is just below, or email me if you prefer. I usually reply within two working days.

Tell me about your projector email me: chendaniel150701@gmail.com

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