System designHardsd-g597

Subject Object storage serviceLevel Senior–Staff~45 minCommon in Databases & SQL · Storage & CDN interviewsIndustries Technology

Question

Design an S3-like object-storage service. Constraints: 11 nines (99.999999999%) of durability, exabyte-scale total capacity, objects from 1 KB to 5 TB, read-heavy at roughly 20:1 read/write, p99 GET latency under 100 ms for warm objects, and strong read-after-write consistency for new PUTs. Walk the request path, the metadata layer, and how you place and protect bytes at this scale.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

Loading whiteboard…

Run or narrate your approach, then ask the coach.