Tangential but I'm a bit blown away by that mongoDB mention - that it just flushes every 100ms, so you can lose writes. The link in the article is invalid, but from https://www.mongodb.com/docs/current/core/journaling/ we see:

"In between write operations, while the journal records remain in the WiredTiger buffers, updates can be lost following a hard shutdown of mongod."

Does Mongodb acknowledge writes as soon as they've hit the buffers or do they wait for an fsync? Because if the former, that's... shocking for a database people use as a source of truth.