At 3:17 a.m. on a Tuesday, my phone buzzed with the alert that would reshape the way I think about API design.
Our customer-facing API had stopped responding. Not slowly degrading; it was completely dead. Three downstream services went with it. By the time I got to my laptop, customer support tickets were flooding in.
The root cause? A single database replica had gone down, and our API had no fallback. One failure cascaded into total unavailability. I spent the next four hours manually rerouting traffic while our customers waited.
That night…
