What is the difference between Redis Pub/Sub and Streams?
Assesses fundamental understanding of Redis 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.
Pub/Sub is fire-and-forget messaging. Publishers send to a channel and subscribers receive in real time, but messages are not stored. An offline subscriber misses them, and there is no acknowledgement or replay. It is simple and fast for live notifications where loss is acceptable.
Streams are a persistent, append-only log. Each entry has an id, and consumers can read ranges, replay history, and use consumer groups for at-least-once delivery with XACK acknowledgements. Pending entries can be claimed by another consumer if one fails, and XADD supports trimming with MAXLEN.
XADD orders * type "created" id 42
XREADGROUP GROUP workers c1 COUNT 10 BLOCK 5000 STREAMS orders >
Use Pub/Sub for ephemeral events and Streams for reliable event processing, audit logs or work queues that must survive restarts.
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.