Redis Cache 면접 질문과 답변
Ques 11. What are the disadvantages/limitations of using Redis?
Following are the disadvantages/ limitations of Redis:
- It is single threaded.
- It has got limited client support for consistent hashing.
- It has significant overhead for persistence.
- It is not deployed widely.
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Ques 12. What is the difference between Redis and RDBMS?
There are a lot of differences between Redis and RDBMS:
- Redis is a NoSQL database while RDBMS is an SQL database.
- Redis follows the key-value structure while RDBMS follows the table structure.
- Redis extremely fast while RDBMS is comparatively slow.
- Redis stores all the dataset in primary memory while RDBMS stores its dataset in secondary memory.
- Redis is generally used to store small and frequently used files while RDBMS is used to store big files.
- Redis provides only official support for Linux, BSD, Mac OS X, Solaris. It doesn?t provide official support for Windows currently while RDBMS provides support for both.
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Ques 13. Differentiate Memcached and Redis?
| Memcached | Redis |
|---|---|
| Memcached only does caching information. | It provides some more functionalities like replication and persistence along with caching information. |
| Memcached supports the functionality of LRU (Least Recently Used) eviction of values. | LRU is not supported by Redis. |
| In Memcached, when they overflow memory, the one you have not used recently (LRU- Least Recently Used) will get deleted. | In Redis, there is a time set for each function, Three keys are maintained, the one, which is closest to expiry, will get deleted. |
| CAS (Check and Set) is supported by Memcached. | CAS is not supported by Redis. |
| Array objects are needed to be serialized in order to get saved. We need to unserialize them for their retrieval. | Redis has got stronger data structures; it can handle strings, binary safe strings, list of binary safe strings, sorted lists, etc. |
| Memcached has at most 250 bytes length. | Redis has at most 2 GB key length. |
| It is Multi-threaded | It is single threaded. |
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Ques 14. Mention Operation Keys of Redis.
- TYPE key
- TTL key
- EXPIRE key seconds
- EXPIREAT key timestamp
- EXISTS key
- DEL key
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Ques 15. Which are the different data types used in Redis?
There are mainly 5 types of data types supported by Redis:
- Strings
- Hashes
- Lists
- Sets
- Sorted Sets
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