Everything you said is incorrect. Redis does have transactions, as well as data persistence. All cloud providers provide managed redis instances with automatic backups as well.
I mentioned that Redis can write changelog (called AOF in the docs [1]). However, if you tell it to do fsync on every update (like SQL databases do), it stops being that fast and spends time waiting for the filesystem.
Furthermore, the RDB snapshot mechanism (when Redis forks and forked process writes the snapshot) can double memory consumption and cause thousands of page faults in Redis process if there are many writes happening.
The docs contains corresponding warnings. "Cloud backups" are marketing terms and not ACID guarantees.
As one more disadvantage, Redis has no SQL and you cannot easily view the data.
As for transactions, indeed it seems to have them, but their execution is serialized, i.e. when MySQL can prepare 100 transactions in parallel, Redis will execute them sequentially.
