Have you ever been hired in too high?

So I prepped quite hard for my recent job search. Some would say I over prepared and landed a senior position that almost doubled my pay. For example, with system design I became good enough that the interviewer was surprised someone with my 3 YOE was doing this well. Now the reality is, on paper I’ll design a flawless system and account for scaling issues etc but in reality I’ve never done this in practice. So I’ve been hired in for a position that requires doing this stuff for real and now I’m kinda unsure if I shot myself in the foot thinking I’ll go in and be exposed. How does one handle this? Any advice would be appreciated.

Concrete example would be: On paper - shard the database, use consistent hashing to distribute nodes In reality - I have no clue how to shard a database and distribute on a hash ring