When would you choose S3 over EBS?
Assesses fundamental understanding of AWS conventions, runtime behavior, and memory/performance considerations.
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Choose S3 when you need durable, virtually unlimited object storage accessible over HTTP from anywhere. Choose EBS when you need a block device attached to a single EC2 instance, such as a database data directory or a boot volume.
Reasons to pick S3:
- Eleven nines of durability across multiple Availability Zones by default.
- Massive scalability and pay-per-use pricing with no pre-provisioning.
- Features such as versioning, lifecycle policies, replication, and event notifications.
- Concurrent access from many clients and services.
Pick EBS for low-latency random I/O, filesystems, and single-instance workloads. EBS volumes are AZ-scoped and usually attach to one instance at a time, although io2 multi-attach exists. Many designs combine them: EBS for the OS and database, S3 for backups, logs, and static assets. Use EFS or FSx when you need shared POSIX file storage.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.