What to ask your agency about database migrations

Most teams know this matters. Fewer have decided who owns it. If you are briefing an agency or a freelancer on database migrations, these questions are worth asking early.

The question is rarely whether something can be built, but what it costs to keep running afterwards. Anything you cannot measure here, you are deciding by taste, which is fine as long as everyone knows it.

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

Migrations should be reversible or provably safe. Getting it slightly wrong is survivable. Ignoring it entirely is not. It rarely shows up as a line item, which is exactly why it slips.

Backwards-compatible changes let you deploy without downtime. Where this goes wrong is almost never a lack of knowledge. If two people in the business would answer this differently, that gap is the actual problem.

The short version

Code gets read far more often than it gets written, and usually by someone with less context than the author had. Three things worth confirming about database migrations before you move on:

• Someone can say what the current setup is without going to look
• Migrations should be reversible or provably safe — and you know whether that is true here
• There is a way to tell whether the last change to this helped

The point is not perfection, it is knowing which of these you have consciously chosen to skip.