Here are some recommendations for your reference:
• If a slow log is generated, you can check the slow SQL log to see if there is any slow SQL query and the corresponding execution plan to locate the cause. To query the MySQL logs,see Viewing Slow Logs.
• Check the CPU usage indicators for RDS for MySQL instances to help locate the cause.
• Create read-only instances for query only, thus reducing the pressure from the primary instance and easing the pressure on the database.
• If the instance specification is small but the load is too high, you can increase the CPU/memory specification. For details,see Specification Scaling.
• Add indexes for associated fields in multi-table association queries.
• Indexes can improve the efficiency of the corresponding SELECT statement. However, this does mean that the more indexes, the better because indexes also reduce the efficiency of INSERT and UPDATE statements. Since INSERT or UPDATE statements will update the index, make careful consideration when you build an index. One table should have up to six indexes as much as possible.
• Avoid large transaction operations to improve the concurrency of the system.
• Do not return a large amount of data to the client. If the amount of data is too large, you should consider whether the corresponding requirements are reasonable.