How many records can Redis handle?

Redis can handle up to 2³² keys, and was tested in practice to handle at least 250 million keys per instance. Every hash, list, set, and sorted set, can hold 2³² elements. In other words your limit is likely the available memory in your system.

Also to know is, how much RAM do I need for Redis?

12 megabytes

Similarly, does Redis keep all data in memory? Redis is an in-memory database because it keeps the whole data set in memory, and answers all queries from memory. Because RAM is faster than disks, this means Redis always has very fast reads. They always keep the whole data set including indices on disk in a format that allows random access.

Also to know is, how many requests per second can Redis handle?

As previously measured, a benchmark setting 100 Bytes values for each key in Redis, would be hard limited by the network at around 32 million queries per second per VM. Even for 1000 Bytes values, Redis would only be hard limited by the network at around 3 million queries per second per VM.

When should you not use Redis?

We will not want to use Redis for use cases like these:

Storing large amounts of data in a single string value (e.g. the most recent feed contents for each user).
Storing data across two or more dimensions (e.g. a score for each (user, topic) pair).
Storing data that requires queries with high time complexity.

38 Related Question Answers Found

What happens when Redis is full?

What happens if Redis runs out of memory? If this limit is reached Redis will start to reply with an error to write commands (but will continue to accept read-only commands), or you can configure it to evict keys when the max memory limit is reached in the case where you are using Redis for caching.

Is Redis in memory only?

5 Answers. Redis is an in-memory but persistent on disk database, so it represents a different trade off where very high write and read speed is achieved with the limitation of data sets that can't be larger than memory.

When should I use Redis?

Top 5 Redis Use Cases

Session Cache. One of the most apparent use cases for Redis is using it as a session cache.
Full Page Cache (FPC) Outside of your basic session tokens, Redis provides a very easy FPC platform to operate in.
Queues.
Leaderboards/Counting.
Pub/Sub.
More Redis Resources.

Can Redis be used as a database?

Redis is an open source (BSD licensed), in-memory data structure store, used as a database, cache and message broker. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs, geospatial indexes with radius queries and streams.

How fast is Redis?

Without Redis, they would've needed to build a 150+ node cluster to support a network speed of 120 Gbps. In addition, they would've required increased work at the application level. Redis works using a six, in-memory, node cluster, 1.5 Gbps, and no extra work at the application level.

Does Redis support SQL?

You cann't use SQL in Redis because it is a memory Database, which unlike most of relational Databases. Please check the documention, that will help you to use it.

Is Redis a key value store?

Redis is an in-memory non-relational key-value store (sometimes referred to as a data structure server). This means that it stores data based on keys and values — think of it as a giant dictionary that uses words and their definitions to store information.

Where is Redis cache stored?

All the cache data will be stored in the memory of the server provided to the config of running redis server. The clients do not hold any data, they only access the data stored by the redis server.

Is Redis faster than MySQL?

Introduction to Redis

Actually, Redis is an advanced key-value store. It is super fast with amazingly high throughput, as it can perform approximately 110000 SETs per second, about 81000 GETs per second. In this article, to have some benchmarks in comparison to MySQL, we will be using Redis as a caching engine only.

Why is Redis so fast?

The ability to work with different types of data is what really makes Redis an especially powerful tool. A key value could be just a string as is used with Memcached. All of the data is stored in RAM, so the speed of this system is phenomenal, often performing even better than Memcached.

Is Redis thread safe?

Enter the Redis GIL

Luckily, Salvatore Sanfilippo has added a revolutionary change just near the finish line of Redis 4.0 and the release of the modules API : Thread Safe Contexts and the Global Lock. The idea is simple. While Redis still remains single threaded, a module can run many threads.

Is Redis server single threaded?

Redis is, mostly, a single-threaded server from the POV of commands execution (actually modern versions of Redis use threads for different things). It is not designed to benefit from multiple CPU cores. It is not really fair to compare one single Redis instance to a multi-threaded data store.

Does Redis save to disk?

By default Redis saves snapshots of the dataset on disk, in a binary file called dump. rdb . You can configure Redis to have it save the dataset every N seconds if there are at least M changes in the dataset, or you can manually call the SAVE or BGSAVE commands.

Is Redis synchronous?

Redis uses asynchronous replication by default: Redis is designed for performances and low, easy to predict, latency. However if possible it is nice for a system to be able to adapt consistency guarantees depending on the kind of write, so some form of synchronous replication could be handy even for Redis.

How do I know if Redis is running?

Check if Redis is working

This program is called redis-cli. Running redis-cli followed by a command name and its arguments will send this command to the Redis instance running on localhost at port 6379. You can change the host and port used by redis-cli, just try the --help option to check the usage information.

How does Redis measure performance?

6 Crucial Redis Monitoring Metrics You Need To Watch

Performance Metric: Throughput. Throughput tells you how many database operations your server is performing in a particular time duration.
Memory Utilization. Memory is a critical resource for Redis performance.
Cache Hit Ratio.
Active Connections.
Evicted/Expired Keys.
Replication Metrics.

How does Redis handle concurrency?

A single-threaded program can definitely provide concurrency at the I/O level by using an I/O (de)multiplexing mechanism and an event loop (which is what Redis does). Parallelism has a cost: with the multiple sockets/multiple cores you can find on modern hardware, synchronization between threads is extremely expensive.