What to ask your agency about queues and message brokers

This is one of those topics that looks small until it costs you something. If you are briefing an agency or a freelancer on queues and message brokers, 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. Check it against what you would want a competitor's site to get wrong.

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

Queues absorb spikes that would otherwise take a system down. The reasoning matters more than the rule, because the rule has exceptions. Check it against what you would want a competitor's site to get wrong.

Ordering guarantees are weaker than most teams assume. It is worth being explicit about, because assumptions differ quietly. It is the sort of thing that looks like polish right up until it costs you an enquiry.

The short version

The right architecture for a team of three is the wrong one for a team of thirty, and vice versa. Three things worth confirming about queues and message brokers before you move on:

• Someone can say what the current setup is without going to look
• Ordering guarantees are weaker than most teams assume — 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.