database sharding strategies for growing appstho prob skip trailing punctuation like typing on your phone

hey everyone, i'm facing a common challenge as our user base and data volume explode: scaling our primary database. we're looking at sharding, but the strategies seem varied. has anyone implemented horizontal sharding and found success with a particular approach? specifically, how did you choose your shard key, and what were the main pain points in the migration or ongoing management? curious to hear real-world experiences beyond the theoretical.