Topic 16.1
Beginner Questions (1–15)
In one line
Fifteen fundamentals every Redis interview can open with: what Redis is, why it's fast, how it compares to PostgreSQL and Memcached, the data types, TTL, eviction, persistence, replication, transactions and pipelining. Short, precise answers with one example each.
Think of it like this
The warm-up questions in a driving test. They're simple, but a shaky answer to "what does this sign mean?" makes the examiner watch everything else more closely. Crisp fundamentals buy you credibility for the hard questions.
Key ideas
- 01
Answer shape for beginner questions: one-sentence definition, one mechanism, one example, one caveat. For example: "TTL makes a key expire; Redis deletes expired keys lazily on access and actively by sampling;
SET session:1 x EX 1800; a plainSETlater removes the TTL unless you useKEEPTTL." - 02
Each question here maps to a topic: Phase 0 (what, why fast), Phase 1 (types), Phase 2 (TTL, eviction), Phase 3 (transactions, pipelining), Phase 9 (persistence), Phase 10 (replication).
- 03
Always mention the caveat: interviewers probe the edge ("fast, but single-threaded, so one slow command blocks everyone").
Explain it without notes
1. What is Redis?
2. Why is Redis fast?
3. Redis vs PostgreSQL?
4. Redis vs Memcached?
5. What data types does Redis have?
6. String vs Hash for an object?
7. List vs Stream?
8. Set vs Sorted Set?
9. What is TTL?
10. What is eviction?
11. What is persistence in Redis?
12. RDB vs AOF?
13. What is replication?
14. What is a Redis transaction?
15. What is pipelining?
Practice
Answer questions 1, 2 and 12 out loud in under 60 seconds each, then compare with the model answers.
Done when you can
I can answer all 15 beginner questions with definition, mechanism, example and caveat.