database sharding strategies for high-traffic apps. dont you hate when apps slow down?

hey everyone, im working on scaling an app that's seeing a serious jump in user traffic. we're hitting some limits with our current monolithic database setup and are considering sharding. there are a few common approaches like range-based, hash-based, and directory-based. what are your go-to strategies when implementing sharding? any specific pitfalls or wins you've encountered with different methods, especially when dealing with complex queries or cross-shard transactions