When do you choose S3, EBS, or EFS in AWS?
Reported in Two Sigma interview loops. Cloud fundamentals question about storage trade-offs.
Interview scenario
Often asked in Two Sigma technical or coding rounds. Prepare a clear spoken answer plus key trade-offs.
Model answer
Try answering aloud first
Cover trade-offs, structure, and a concrete example before revealing the baseline response.
How to frame this at Two Sigma: Connect your answer to measurable impact, clarity of thought, and trade-offs the team cares about. Below is a strong baseline response you can adapt with your own project examples.
S3 is object storage, durable and cost-effective for files, backups, and static assets. It is not a POSIX file system and has different access patterns than mounted disks.
EBS is block storage attached to a single EC2 instance at a time, ideal for databases and low-latency persistent volumes. EFS is managed network file storage shared by multiple instances for POSIX-style access.
A complete answer links choice to latency, throughput, sharing model, consistency needs, and cost.
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