Integrating with an external service.
WHAT TO ESTABLISH FIRST
What you actually need from it.
WHAT TO READ BEFORE CODING
Authentication Rate limits Error behaviour Whether a sandbox exists The terms of use
WHY THE TERMS SPECIFICALLY
They constrain what you may store, display and do.
WHAT TO BUILD FIRST
One successful call, by hand, from the command line.
WHY BY HAND
It separates interface problems from your code.
WHAT TO WRAP IT IN
A client of your own, rather than calls scattered through the application.
WHAT THAT PROVIDES
One place for authentication, retries, logging and error translation The ability to replace the provider
WHAT TO HANDLE
Timeouts Rate limiting Errors of every class Responses that are not what was documented
WHY THAT LAST POINT
Interfaces return undocumented shapes more often than anyone admits.
WHAT TO NEVER ASSUME
That a field will always be present That the response will always parse That the service will be available
WHAT TO SET
A timeout on every call.
WHY
Without one, a hanging call ties up your own resources indefinitely.
WHAT TO LOG
The request, the response status, and the time taken.
WHAT TO MONITOR
Error rates and latency, per provider.
