The Mixed PR Queue: Reviewer Throughput Is Now the Binding Constraint
For the last twenty years, the Theory of Constraints answer in software delivery was the same: the bottleneck is producing code. We tooled around that assumption — pair programming, IDE autocompletion, faster CI, smaller services, all designed to push more code through a fixed-width review pipe. Then coding agents arrived, the production side of the pipe got 5–10x wider, and the review pipe stayed exactly the same width. A senior engineer who used to open three PRs a week now supervises a fleet that opens thirty in an afternoon. The team's velocity is no longer set by how fast anyone writes code. It's set by how fast a human can read it.
This is not a future problem. Median PR review time has been measured at +441% year over year in some samples, and 31% more PRs are merging with zero review — not by policy, but because reviewers gave up trying to keep pace. Stripe is shipping over a thousand agent-produced PRs per week. Feature-branch throughput grew 59% YoY in one benchmark while main-branch throughput fell 7% — code is being written, but it's not getting promoted, because it's stuck in review.
