What to ask your agency about idempotency

Teams tend to reach for this after something has already gone wrong. If you are briefing an agency or a freelancer on idempotency, these questions are worth asking early.

Architecture is the set of decisions that are expensive to reverse, which is the only reason they deserve the name. Assume whoever inherits this will have half your context and none of your patience.

Questions worth asking

• Who will actually do this work, and have they done it before?
• How will we know afterwards whether it worked?
• What happens if it needs changing in a year?
• What are you assuming that we have not confirmed?

What a good answer sounds like

Networks retry, so assume every request can arrive twice. That sounds obvious written down. It is still the thing most often skipped. Doing this properly once is usually cheaper than doing it approximately three times.

Payment and order endpoints are where this matters most. That sounds obvious written down. It is still the thing most often skipped. Doing this properly once is usually cheaper than doing it approximately three times.

What this looks like day to day

Most systems fail at the seams rather than inside any one component. Three things worth confirming about idempotency before you move on:

• Someone can say what the current setup is without going to look
• Payment and order endpoints are where this matters most — and you know whether that is true here
• There is a way to tell whether the last change to this helped

If you want a second opinion on how yours is set up, ask.