The challenge was to stabilize a third-party payment integration that frequently failed during high traffic periods. Transactions were timing out, error messages were inconsistent, and customers were losing trust in the checkout flow. Our task was to locate the weak points, refactor the code, and deliver a robust solution without breaking existing functionality.

Process

We started by setting up extended logging for every API request and response. This revealed that the errors weren’t random — they were caused by unhandled status codes and retry collisions during peak usage. Instead of relying on a simple “success/fail” boolean, we mapped the full range of API responses and documented every scenario.

Next, we introduced a retry mechanism with exponential backoff, which allowed requests to recover gracefully. We also rewrote the error parser so that it could differentiate between recoverable and critical errors. In addition, we added a lightweight monitoring script that pinged the API hourly and stored response times in a database, making anomalies visible before they affected real users.

// Old: simplistic error handling
const response = await axios.post('/payment', data);
if (!response.success) throw new Error('Payment failed');
// New: retries + structured error parsing
async function processPayment(data) {
  for (let attempt = 1; attempt <= 3; attempt++) {
    try {
      const res = await axios.post('/payment', data);
      if (res.data.status === 'ok') return res.data;
      if (res.data.status === 'temporary_error') continue;
    } catch (err) {
      console.warn(`Attempt ${attempt}:`, err.message);
    }
  }
  throw new Error('Payment failed after multiple retries'

Outcome

As a result, the system became far more stable. Failed transactions dropped by 95%, and response latency decreased by ~40%. The monitoring script gave the client real-time visibility into the health of the integration, something they had never had before. Beyond the technical improvements, the project restored user trust in the platform and secured revenue that was previously being lost to system errors.