One approach Cloud Infra team took to reduce cost of infra in tvlk-prod account, was to identify and delete unused snapshots. We think it's a quick and easy way to reduce cost.
Unused snapshots are periodic database backups (MongoDB & RDS) that are no longer needed because database has been decommissioned or migrated into another AWS account.
On April 6, 2020, we removed thousands of unused snapshots from tvlk-prod account. This reduced our snapshot usage by 1,544.85 GB-month per day, resulting in $67.20 per day or $2,016 per month in savings.
We think this approach can be applied to other AWS accounts as well, so to help you try the same approach with minimal effort, Cloud Infra team has created a script to help identify unused snapshots.
You can take a look at the script at this repo: https://github.com/traveloka/AWS-Cost-Optimization-Tools/. Feel free to contribute or throw some ideas in the repo.