* = if read only mode is not considered “downtime” for you
If you have a giant database then upgrading your site could take anywhere from 10 to 60 minutes. A significant chunk of this goes in backup, schema migration, and patches. All of which require disabling writes on the database.
I’ve been working on reducing downtimes during upgrades, while we are yet to have super fancy and complex systems where writes are just moved to a separate system and “merged” later… what we can easily get is “read only” mode on sites. This does reduce “downtime” for many users or at least lessens the impact of downtime as you can still view things and work on them.
This feature is still a few weeks and a few reviews away before it lands in v14 but if you’re a developer or care about this stuff you can test it out on test sites by checking out this PR:
docs for setup: Zero* downtime migrations
Here’s how it looks btw: