What all technologies I should know if applying for SDE-2/3 (Backend) around 4yr+ experience

Comp between 25 to 40 in product companies (not considering big tech and best paymasters)

You should know, not only prepare for interviews. Anyways it's required after joining.

• at least one more language, python/go/java may be
• web frameworks and their needs (nextjs for example). Similar frameworks in other languages
• cloud native
• database design and choice of DB
• prompt engineering (may be become mandatory soon)
• scaling systems in service, cache, DB (good to start with this)

*started my career