| DataStructure |
String |
String, List, set, sorted set, hash etc |
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| Persisiance |
Not supported |
AOF (append only file) |
The AOF Log stores all of these commands in the same format Redis receives them |
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AOF log is better if data loss is not acceptable at all, as it can be updated at every command. |
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RDB (redis db backup) |
full snapshot of the current Redis state by child process |
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in Redis is too big, the RDB file will take some time to be created, which has an impact on the response time. On the other hand, it will be faster to load on boot up compared to the AOF log. |
| Data Eviction policies |
LRU |
NO EVECTION |
returning an error the memory limit is reached |
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All keys LRU |
removing keys by the least recently used first |
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VOLATILE LRU |
removing keys, that have an expiration time set by LRU |
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All keys Random |
removing keys randomly |
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Volatile random |
removing keys, that have an expiration time set, randomly |
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VOLATILE TTL |
removing keys, that have an expiration time set, by the shortest TTL first. |
| Multithreading |
Multi |
Singhle, (multi after Redis6) |
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| Key Value |
250 Bytes |
512MB upto |
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| |
1MB default value |
Value could be jpeg img |
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| Replication |
supported by3rd party s/w |
Natively |
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| Clustering |
Not supported nativley |
Redis cluster |
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| Use Case |
Extermley simple application, limited server, and only String representation |
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| Why Redis is Fast |
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Becoz, single threaded (using non blocking multiplexing IO , epool implementation) |