I recently finished the MIT distributed systems labs and wrote up one Raft rule that took me some time to fully understand: why a leader cannot safely commit old-term entries just because they’re replicated on a majority.

When reading the paper, this can feel like a detail you just accept and move on from. But during implementation/debugging, it becomes much more concrete. You start seeing why “replicated on a majority” is not enough by itself, and why the current-term restriction matters for safety.

I tried to explain it from the perspective of someone implementing and debugging Raft, not just restating the theory.

Article: https://abdellani.dev/posts/2026-03-23-why-raft-cant-safely-commit-old-term-entries/

I’d be curious how this clicked for others:
did it make sense immediately from the Raft paper, or only after implementing/debugging it?