How do you choose the right storage solution for a given workload?
What they are really testing: Senior signal: starts from the access pattern and requirements (latency, durability, scale, cost) rather than defaulting to a favorite, and maps object/block/file/database to the right job.
A real interview question
How do you choose the right storage solution for a given workload?
What most people say
drag me
“I would use object storage like S3 because it is cheap and scalable.”
Defaulting to one option ignores the workload. Object storage is wrong for a low-latency transactional database (that needs block) or shared POSIX access (that needs file). A senior starts from access pattern and requirements, not a favorite.
The follow-ups they ask next
Why is object storage a poor fit for a transactional database?
It is not low-latency random-access and lacks filesystem semantics; databases need fast random I/O and block-level access, so they want block storage (provisioned IOPS). Object storage suits blobs/static/scale, not a DB data directory.
When would you combine multiple storage types in one system?
When different data has different needs, e.g. block storage for the database, object storage for user uploads, a CDN for static assets. You match each data type to the right store rather than forcing one everywhere.
What the interviewer is listening for
- Starts from access pattern + requirements
- Maps object/block/file/database to the right job
- Avoids defaulting, combines types when needed
What sinks the answer
- Defaults to one favorite store
- Ignores access pattern/latency
- Would put a DB on object storage
If you genuinely do not know
Say this instead of freezing. Reasoning out loud from what you do know beats silence every single time, and a good interviewer is listening for exactly that.
“Start from [the access pattern: random vs sequential, read/write-heavy, latency-sensitive, shared or single]. Map it: [object storage for large blobs/static/scale, block for low-latency single-attached DBs/OS disks, file for shared POSIX, a database for structured/queried data]. Weigh [durability, scale, latency, cost]. Do not [default to a favorite], and [combine types when different data has different needs].”
Keep going with storage
Foundation
What is the difference between durability and availability for storage?
Foundation
What is the difference between backup and replication, and why is replication not a backup?
Junior
Explain the difference between object, block, and file storage, and give one good use case for each.
Junior
How does object storage achieve such high durability?
Junior
What consistency guarantees does object storage give, and why does it matter?
Junior
For block storage, what is the difference between IOPS and throughput, and how does it affect volume choice?
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