The setup you describe is very much not simple. I worked at a place with very good DBAs and our replication setup caused us more downtime than anything else. Cockroach and Spanner exist because many programmers observed that what you describe is hard.

As a counter-anecdote: multiple startup projects I've worked on with separate MySQL setups where each had just a single master + two slaves (one warm for fast failover in case of hardware failure or upgrades, one cold for slow analytics-style queries) did just fine with millions (to tens of millions) of users. No downtime at all for years on end.

MySQL and Postgres are massively more widely-used than Cockroach and Spanner, broadly very successfully. It's entirely feasible to run it with high uptime.

Very few deployments experience actual failures. Could be some fridge-door/light situation going on.

> fridge-door/light situation going on

what does it mean ?

I think that is meant to be parsed as: Just like you can't check if the fridge light is on without opening the door (which of course turns it on), it's hard to know if a system is resilient to failure without having one. It just might be that there hasn't been a situation that would cause a failure.