Primary Key design is an important thing for InnoDB performance, and choosing a poor PK definition will have an impact on performance and also write propagation in databases. When this comes to Aurora, this impact is even worse than you may notice. In short, we consider a poor definition of a Primary Key in InnoDB [&]

https://www.percona.com/blog/making-aurora-write-latency-15x-higher-or-more-by-choosing-a-bad-primary-key/