Aws RDS Queries working slow after schema import and dump

Question

I have a t3.small instance for my database I was inserting records after adding indexes to a table using a script, the script is expected to run around for 18 minutes and insert the records, at the same time I imported another schema which is 1.8 GB my existing schema is 1.3 GB, afterward the queries got slow then I deleted the new imported schema still for whole one day the queries were slow, want to know the reason behind this as t3.small has storage of 20 GB, I checked the metrics for these parameters at that time DiskQueueDepth, BurstBalance was low, BinLogDiskUsage was high. I Want to avoid this in the future as it incurs downtime and timeout for the APIs.