100% uptime is impossible of course, a 100% reliable service would survive the next ice age.

But reliability at the holy grails of 4 and 5 nines (99.99%, 99.999% uptime) means ever greater investment - geographically dispersing your service, distributed systems, dealing with clock drift, multi master, eventual consistency, replication, sharding.. it’s a long list.

Questions to ask: could you do better yourself - with the resources you have? Is it worth the investment of a migration to get there? Whats the payoff period for that extra sliver of uptime? Will it cost you in focus over the longer term? Is the extra uptime worth all those costs?