Dive Deep: Complex Project Involvement

Situation

Our customer support team was reporting a spike in refund requests due to failed invoice generation in our billing system. It was affecting trust and revenue. The billing system was owned by another team, but the issue seemed to start after our product team released a new subscription plan.

There was finger-pointing across teams. I volunteered to investigate, even though it wasn’t “my system.”

Task

My goal was to uncover the root cause, document the dependencies, and drive a fix — fast. The problem was buried across 3 microservices, with no single owner and logs split across multiple environments.

Action

I started tracing failed invoice IDs from customer records through the billing database, into the queue service, and all the way back to our pricing config. I discovered a silent failure in the plan mapping logic — new SKUs weren’t being serialized correctly due to a version mismatch between our app and the billing queue schema.

• 🔍 Queried invoice IDs with no payment tokens
• 🔧 Reproduced issue in staging by simulating new plan behavior
• 📈 Correlated failure timestamps with deploy logs to identify version drift

// Example: silent serialization bug
  const sku = planConfig[planId]; // undefined for new plan
  enqueueInvoice({ sku }); // No error thrown → downstream processing fails
      

I fixed the plan mapping, added validation logic before enqueue, and backfilled the broken invoices via a script after syncing with billing ops.

Result

Refund requests dropped by 87% within 48 hours. I wrote a postmortem shared org-wide and introduced a shared schema test in CI to prevent future mismatches. The incident became a case study in our engineering wiki under “Cross-System Debugging: A Deep Dive.”

This led to me being invited into a cross-team reliability council — and built strong trust across domains I didn’t formally own.

Reflection

• 🛠️ Deep dives don’t start with answers — they start with curiosity.
• 📚 Ownership isn’t defined by org charts — it’s defined by who’s willing to investigate.
• 🔁 Understanding systems end-to-end helps prevent future fires, not just fix them.

FAQ