Optimize AWS MySQL RDS Performance

I'm currently facing a high load issue on my AWS MySQL RDS instance, which is affecting both read and write queries. Despite not having made any recent changes to the database or application, the system is under stress, operating at about 90% capacity. The slow performance is becoming increasingly problematic and I need an expert to help diagnose and resolve this issue as quickly as possible.

Ideal Skills:
- Extensive experience with AWS and MySQL.
- Proficient in diagnosing high load issues.
- Skilled in query optimization.

Please, only bid if you can demonstrate relevant experience and can deliver a timely solution.