Memcached is a general-purpose distributed memory caching system. It is often used to speed up dynamic database-driven websites by caching data and objects in RAM to reduce the number of times an external data source (such as a database or API) must be read.
Redis is a flexible, open source and advanced key-value store. It is referred to as a “data structure server” where keys can contain strings, lists, hashes, sets and sorted sets of strings.
The main differences between them are listed below:
Installation:
Comparing ease of Installation Redis is much easier. No dependencies required.
Memory Usage:
For simple key-value pairs memcached is more memory efficient than Redis. If you use Redis hashes, then Redis is more memory efficient.
Persistence:
If you are using Memcached then data is lost with a restart and rebuilding cache is a costly process. On the other hand, Redis can handle persistent data. By default, Redis syncs data to the disk at least every 2 seconds.
Replication:
Memcached does not supports replication. Whereas Redis supports master-slave replication. It allows slave Redis servers to be exact copies of master servers. Data from any Redis server can replicate to any number of slaves.
Storage type:
Memcached stores variables in it’s memory. It retrieve any information directly from the servers memory instead of hitting the database again. On the other hand, Redis is like a database that resides in memory. It executes (read and write) a key/value pair from its database to return the resultset and all data resides in memory.Developers are using Redis also for real-time metrics, analytics.
Read/Write Speed:
Memcached is very good to handle high traffic websites. It can read lots of information at a time and give you back at a great response time. Redis can also handle high traffic on read but also can handle heavy writes as well.
Data Structure:
Memcached uses string and integer as data structure. Everything you save can be either one or the other. With integer, the only data manipulation you can do is adding or subtracting them. If you need to save arrays or objects, you will have to serialize them first and then save them. To read them back, you will need to un-serialize.
In comparison Redis has a stronger data structures. It can handle not only strings, integer but also binary-safe strings, lists of binary-safe strings, sets of binary-safe strings and sorted sets.
Key Length:
Memcached key length has a maximum of 250 bytes, whereas Redis key length has a maximum of 2GB.
If you need advanced data structures or disk-backed persistence, you should look into Redis. On the other hand, you might want to stick to Memcached for its simplicity, reliability and speed.
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