We keep recently fetched files on the EC2 instance's EBS volume for a few days (or until they are evicted to make space), as this is faster than re-reading them

We keep recently fetched files on the EC2 instance's EBS volume for a few days (or until they are evicted to make space), as this is faster than re-reading them from S3 each time someone does a search, and it's common to do a number of searches over the same time period when debugging an issue.