You will get a payment flow audit for double-charges and race conditions
Project details
Payment bugs are quiet. Nothing crashes, no error appears in your logs, and the first sign of trouble is a customer emailing to say they were charged twice. By then the money has moved and the fix is a refund plus an apology.
I review your payment code specifically for the failure modes that cost money: handlers that process the same event more than once, race conditions where two requests read the same balance before either writes, missing reconciliation between your database and your provider, and state transitions that let an order reach an impossible status.
You get a written report listing every issue found, ranked by severity, with the exact file and line involved and a recommended fix for each. Not a generic checklist. Findings from your actual code.
I have spent 7+ years building payment systems, including cross-border remittance, escrow and refund logic, and subscription billing for a US SaaS platform. I also wrote stateledger, an open-source library for modelling payment workflows as state machines.
If I find nothing serious, I will tell you that plainly rather than padding the report.
I review your payment code specifically for the failure modes that cost money: handlers that process the same event more than once, race conditions where two requests read the same balance before either writes, missing reconciliation between your database and your provider, and state transitions that let an order reach an impossible status.
You get a written report listing every issue found, ranked by severity, with the exact file and line involved and a recommended fix for each. Not a generic checklist. Findings from your actual code.
I have spent 7+ years building payment systems, including cross-border remittance, escrow and refund logic, and subscription billing for a US SaaS platform. I also wrote stateledger, an open-source library for modelling payment workflows as state machines.
If I find nothing serious, I will tell you that plainly rather than padding the report.
Programming Languages
JavaScript, Python, TypeScriptCoding Expertise
Performance Optimization, SecurityWhat's included
| Service Tiers |
Starter
$99
|
Standard
$299
|
Advanced
$799
|
|---|---|---|---|
| Delivery Time | 2 days | 4 days | 5 days |
Number of Revisions | 1 | 2 | 3 |
Design Customization | - | - | - |
Content Upload | - | - | - |
Responsive Design | - | - | - |
Source Code | - |
Optional add-ons
You can add these on the next page.
Follow-up review after fixes
(+ 2 Days)
+$100Frequently asked questions
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MS
Mbongayah S.
Apr 18, 2023
In need of a Web developer
Enow Divine is a skilled and wonderful person with great personality and work ethics. He did his job excellently well and on time, and even notifies me early enough if he thinks a task may take a longer time period and also provide me with details why it will take longer than expected. I think his a great person to work with and would hire him again if I need his services.
About Enow Divine
Senior Full-Stack Engineer | Node.js, TypeScript, React | Payments
Douala, Cameroon - 12:22 pm local time
Payments are where small bugs get expensive. A duplicated webhook. A race condition on a balance. A field rename that silently changes the meaning of a transaction.
I've spent 7+ years building systems designed to prevent those problems: idempotent payment flows, immutable audit trails, and state machines that keep transactions consistent under load.
What I do
* Payment integrations: card processors, mobile money, and multi-currency remittance corridors
* Node.js / TypeScript backends using REST and event-driven architectures, with PostgreSQL and Prisma
* Microservice architecture. I currently own the backend across 15+ services for a US-based multi-tenant SaaS platform
* Full-stack delivery when needed with Next.js, React, and React Native
Things I've built and shipped publicly
* stateledger: a TypeScript state machine library for payment workflows, published on npm and GitHub
* PulseLab: a webhook and WebSocket debugger for developers
* SS Invoice: mobile money invoicing for small businesses
The code is part of the portfolio. You can look through it before you hire me.
Recent client work
* Multi-corridor remittance platform covering Bahrain, the UK, Ukraine, and Canada to Cameroon, with live FX rates, admin approval flows, and proof-of-payment handling
* Event ticketing platform with payment splits and payouts
* Education pathways platform for a licensed Cameroonian company
* Additional client work under confidentiality. I'm happy to walk through the architecture on a call.
Stack
Node.js · TypeScript · NestJS · Express · PostgreSQL · Prisma · Next.js · React · React Native · Redis · Docker · AWS
I work remotely with US and EU teams and usually respond within a few hours.
I'm also comfortable saying when a scope is unrealistic. I'd rather catch that before development starts than discover it three weeks into the project.
If you're building something where money changes hands, send me the details. I'll tell you honestly whether I'm the right fit.
Steps for completing your project
After purchasing the project, send requirements so Enow Divine can start the project.
Delivery time starts when Enow Divine receives requirements from you.
Enow Divine works on your project following the steps below.
Revisions may occur after the delivery date.
Understand the flow
I map how money moves through your system, from the customer action to the provider callback to the final database write, so I know what correct looks like before judging the code.
Audit the code
I go through the payment paths looking for non-idempotent handlers, race conditions, missing reconciliation, and unsafe state transitions. Every finding is tied to a specific file and line.