Design RSS Feed and Temporary Mail
Company: Confluent
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
This interview included two system design prompts.
1. **Design an RSS feed platform**
Design a service that periodically ingests RSS or similar publisher feeds, normalizes the content, and serves feed items to different clients such as web, mobile, and external integrations. Discuss:
- public API design
- when REST is preferable to RPC and when RPC is preferable internally
- versioning and backward compatibility
- caching and freshness
- how to support clients with different capabilities and payload needs
2. **Design a temporary email service**
Design a temporary mailbox system for roughly **100 million users**. Focus especially on:
- generating human-readable email aliases
- checking alias availability and deduplicating quickly at large scale
- whether a Bloom filter is appropriate and how false positives affect the design
If helpful, also cover mailbox lifecycle, inbound email ingestion, expiration, storage, and abuse prevention.
Quick Answer: This question evaluates skills in large-scale system design, covering API design, ingestion and normalization pipelines, caching and freshness trade-offs, versioning and backward compatibility, client-specific payload strategies, scalability and deduplication for alias generation, and the use of probabilistic data structures for temporary email services. It is commonly asked to assess architecture-level trade-offs and operational concerns such as performance, storage, consistency and abuse prevention; the domain is System Design and the level of abstraction spans both conceptual architectural reasoning and practical application-level considerations.