Optimize SQL Table and Queries

I am developing a workload in AWS that stores data in PostgreSQL. A lot of compute instances get spun up at the same time. These compute instances are attempting to retrieve representations of a workload from the database (a single table) at the same time. When doing that, the database is getting overloaded I believe due to a poorly-constructed database and/or a poorly-constructed query to retrieve the work. I would like some help optimizing one or both of them in order to relieve the burden on the database when all of these workers spin up. I can provide a more comprehensive explanation to anyone that is interested in working it. Native-English speakers only, please. This project is going to require a lot of explanation almost certainly, and that is going to be much easier with a native English speaker. To prove you're not a bot, let me know your favorite food in your bid. People who have experience in AWS RDS and/or Lambda will be preferred. Thank you.