Code review
Code review has another engineer evaluate proposed changes before they merge. It catches bugs, enforces style consistency, distributes knowledge across the team, and surfaces design issues before they ship. Code review is the single most-cited engineering activity in DORA research as a marker of high-performing teams.
Effective code review focuses on the things the author can't easily check alone: correctness in edge cases, readability for someone with less context, security implications, and whether the change is the smallest one that solves the problem. Reviews that focus on style nits or personal preferences slow teams down without improving quality, most teams move style enforcement to automated linters specifically to free review for higher-leverage feedback. Async review is the norm but high-stakes changes benefit from a synchronous walkthrough.