Spotify moved the bottleneck and said so

Jo Kelly-Fenton and Aleksandar Mitic at QCon London on Honk, the agent Spotify built to do fleet-wide migrations across thousands of codebases.

The numbers are the kind that make executives forward the slide deck. A migration that reached 70% adoption in nearly a year, with the last 30% never finishing — the long tail everyone has and nobody talks about. With fleet tooling, under a week. With Honk reachable from Slack, they went from a thousand merged pull requests in three months to the same volume in ten days.

Take that seriously. This is the strongest case for coding agents I have seen presented with real figures attached: not novel feature work, but the enormous volume of unglamorous maintenance that never gets done because no one can justify a quarter of dependency bumps. That work is real, it is expensive to neglect, and it is close to ideal for an agent — mechanical, verifiable, and boring enough that no one's craft is offended.

Then, in the lessons, this:

PR review is now the bottleneck, not code generation.

They moved it. They know they moved it. They are up front that standardisation was the biggest lever, that summarising build failures with a model beat parsing output, and — the detail I respect most — that skipping integration tests early on left validation gaps.

A thousand pull requests in ten days is a triumph of generation and a verification bill someone is paying. Spotify have the monorepo, the golden standards and the CI to absorb it, which is exactly DORA's point about AI amplifying whatever system it lands in. Run Honk against an estate without those and you would not get ten days of migrations. You would get a thousand pull requests nobody can review, which is what open source maintainers have been describing all year, only with a budget behind it.

Worth watching in full if you are anywhere near a large migration.