← Icechunk, illustrated

The race condition

Three writer processes race to update the same chunked image. Each lap, every team uploads a fresh photo of its own racer to say "we're in the lead". But the writes overlap in time...

• Zarr: every chunk write lands on the shared array immediately, so three concurrent uploads interleave into a patchwork of all three racers. Often who is leading is undefined!
• Icechunk: each writer stages its upload in a private session, then commits it atomically. The main snapshot is only ever one whole racer, so the leader is always clear, and past leaders stay in the commit history.