Would CRUD operations get very slow on an mysql innodb table which got more than 50 million rows?
I have seen a billion-row table hum along fine.

I have seen a thousand-row table cause the bones of the server to creak and groan.

It all depends on the queries.

"several thousand transactions per day" -- No Problem.  "several thousand transactions per second" -- This gets somewhat challenging, but probably doable.

What to do?


Provide SHOW CREATE TABLE
Provide the main queries.
Provide the main transactions.
Don't do COUNT(*)
Don't do anything that requires hitting all 50M rows -- ask for help in reformulating such queries.


If this is really a financial institution, be sure to hire a security consultant.  You do not want the hassle you will get if the data is lost/stolen.