Feeling quite lost, how hard is the work of a backend engineer in a top MNC?

Hi, I've been working as a data scientist and currently have a 2 yoe in a product based b2b startup(directly joined from college). But almost everything I've done here is a job of a SDE, and now I'm looking for a switch. I think I'm good in DSA/LLD and have been repreparing for it from last few months.

But the problem is, the quality of software engineering work here is really not upto the mark, everything I worked upon was mostly from scratch, so I don't have the experience of working with an existing large codebase.

Secondly, although the features I got to work on sound fancy but I don't think they were much challenging , it was some API doing normal DB operations etc. There was also some work on building some satellite imagery and some other data downloading, storing and fetching services. Even those were mostly about DB operations. Thirdly, the startup I work in doesn't have much requirement of writing proper test cases, or writing very modular code (although I try to write as much as possible), neither the APIs faced much scale issues (as it's a b2b startup and the APIs here really don't face that amount of scale which many of the other companies I heard of face)

I did learn a lot of some of the most used AWS related services, as I also got to work on building deployment pipelines over kubernetes etc.

But in general I'm very much in fear if I would be doing good if I join any good company especially the MNCs as a SDE-1/2. I do feel I can clear the DSA+LLD interviews and maybe even the beginner level HLD interviews (which are asked at my experience level) but I feel quite inferior to the crowd who will be working there and I might even not match the requirements/quality of my peers properly in the starting.

Backend tech stacks I worked on: spring-boot(20%), python-fastapi/flask/django(80%) and also have worked with postgres and mongoDB.

Feeling very lost here, can anyone suggest any way such that along with interview preparation, I also get a much better developer who can actually start contributing in the bigger companies and not considered as a liability and get laid off later.