Take-home assignment: benchmark CognoDB against a handful of other graph databases, fairly. The fairness rule was blunt — every database gets the same tiny resource cap, 0.5 vCPU, 256MB RAM, no exceptions.
Easy to say. Two platforms didn't survive it.
Memgraph kept getting killed by the Linux OOM reaper mid-import. First guess was a missing index. Wrong, checked, fixed, still died. Second guess was storage mode. Memgraph's analytical mode skips the write-ahead log for faster imports, sounded promising. Turns out it also doesn't support the uniqueness constraint the benchmark required — you get one or the other, not both. Back to the normal mode, ran it clean, one more time, just to check.
Killed again. Two clean failures with the config right isn't bad luck. It's Memgraph's in-memory transactional engine having a real memory floor a 256MB box can't clear.
ArangoDB failed for a completely different reason. Buried in its docs: it doesn't actually detect a Docker container's memory limit unless you tell it explicitly. Left alone, it sizes its internal cache off the host machine's RAM, not the container's. Set the override, got further, still died.
