Redis FAQs

General Questions

  • What is Redis?
    • Redis Ltd. is a computer software company located in Mountain View California that is the sponsor of open-source Redis, an in-memory NoSQL database.
  • What does Redis do?
    • Redis (the database) is an in-memory data structure store, used as a database, cache, and message broker. It’s available both as open source and with an enterprise version which is, naturally, even more powerful.

      Redis (the company) enhanced Redis open source with a technology layer that encapsulates the open source version while fully supporting all its commands, data structures, and modules. Redis Enterprise adds exceptional flexibility, stable high performance, and unmatched resilience, as well as multiple deployment choices (public and private clouds, on-premises, hybrid, RAM-Flash combination), topology (active-active, active-passive, active-replica), and support for very large datasets.
  • How do you pronounce Redis?
    • Redis is pronounced “reh-duhs”. Think the color “red” and the pronoun “us” said quickly together.
  • What does Redis stand for?
    • Redis stands for “Remote Dictionary Server”.

Redis Open Source vs. Redis Enterprise

  • What’s the difference between Redis Enterprise and Redis Open Source?
    • Redis Cloud overcomes Redis open source’s limitations. It provides scalable Redis even for dataset sizes beyond the size of the largest server. Moreover, it scales without the hassle of dealing with nodes and clusters, and while maintaining the same endpoints.

      Achieving true high-availability is easy with Redis Cloud. With a click of a button, you can set up in-memory replication (in the same data center or across data centers), data persistence, or remote backups.

      Redis Cloud also shields Redis datasets from virtual environment “noisy neighbors,” resulting in stable, predictable performance.

      The service is fully automated, so you do not need to worry about scaling or recovery from failures.
  • Is Redis Enterprise fully compatible with Redis open source?
    • Yes. Not only are we the home of Redis, but most of Redis’ core engineers also work for Redis! We contribute extensively to the open source Redis project. We adhere to the open source version’s specifications and make every effort to update our service with its latest versions.

      That said, the following Redis features are not applicable in the context of our service:

      Shared databases aren’t supported in Redis Enterprise given their potential negative impact on performance. We recommend using dedicated databases instead. Therefore, the following commands are blocked in the Enterprise version, and produce an error when invoked:

      Data persistence and backups are managed from the service’s web interface, so the following commands are blocked:

      Since replication is managed automatically by the service and since it could present a security risk, the following commands are blocked:

      Redis clustering technology is different from the open source Redis cluster. It supports clustering in a seamless manner that works with all standard Redis clients. As a result, all cluster-related commands are blocked and produce an error when invoked.

      Commands that aren’t relevant for a hosted Redis service are blocked:

      Additionally, only a subset of Redis’ configuration settings (via CONFIG GET/SET) is applicable to Redis Cloud. Attempts to get or set a configuration parameter that isn’t included in the following list results in an error:
      slowlog-log-slower-than (value must be larger than 1000)
      slowlog-max-len (value must be between 128 and 1024)

      Lastly, unlike Redis’ 512MB limit, the maximum size of key names in our service is 64KB. Key values, however, can have sizes up to 512MB.
  • Can I export my Redis data from Redis Enterprise?
    • Absolutely! There is no lock-in with Redis Enterprise . With the click of a button you can export your latest RDB backup file to AWS S3, FTP, or a HTTP server.
  • I use Redis open source. Why should I switch to Redis Enterprise?
    • Self-managing a cluster of open source Redis servers can be a demanding task, especially when datasets are large. The ongoing operation of scaling/clustering/re-sharding/rebalancing, HA settings, recovery from failures and stabilizing performance can be quite error prone, and requires skilled personnel.

      Redis Enterprise removes the heavy lifting from your DevOps/DBAs. All database operations are managed in a near fully-automated manner by our Redis experts, which assures uninterrupted database operation.

      Redis Enterprise completely hides the fact that a Redis cluster is running behind the scenes. Our production-proven zero-latency proxy resides on each node of the cluster. It allows the application to access a Redis cluster as if it were accessing a single Redis instance, so there is no need to change your application code, your clients, or to limit yourself to cluster-specific Redis commands.

      Redis Enterprise also means great savings on cloud resources. You can deploy it on Flash (based on high IOPS SSD instances) and enjoy the same sub-millisecond latencies one experiences using Redis on RAM, while reducing cloud resources cost by over 70%. If your dataset is larger than 500GB, running Redis in a fully-automated manner with 24/7 expert support over Redis Enterprise is lower in cost than managing your own Redis instances on the cloud.
  • What am I allowed to do with the free version of Redis?
    • You can use the full capabilities of Redis Enterprise with the free version, but you cannot deploy it to production. It allows a maximum of four shards and does not provide the same support options as the paid version. The free version of Redis has a 14-day time limit, after which no more configuration changes can be applied. Finally, no SLA is provided with the free version.
  • I use Redis open source. Why should I switch to Redis Enterprise Software?
    • Redis Enterprise helps you overcome the limitations of Redis open source. It provides scalable Redis databases, even for datasets larger than the largest server. Moreover, it scales without the hassle of setting up or dealing with nodes and clusters, without any downtime or application changes while maintaining the same endpoints.

      Achieving true high-availability is easy with Redis Enterprise Software. At the click of a button, you can set up in-memory replication, data persistence, and remote backups. Redis Enterprise protects against every type of outage with instant automatic failover and zero data loss.

      Redis Enterprise also shields your Redis dataset from virtual environment noises, resulting in stable and predictable top performance.And last but not least – it is fully automated, so there is minimal operational overhead with scaling or recovery from failures.

Technical Questions

  • Is Redis Enterprise data safe and always available?
    • Absolutely! Redis Enterprise offers a comprehensive suite of high-availability provisions, including in-memory replication (within the same data center or across data centers), persistent storage on EBS, and backups to S3 or any file server.Read more about Highly-Available In-Memory Cloud Datastores.
  • How do I control access to my resources?
    • Redis Enterprise has several access control mechanisms:
      Password authentication
      Source IP/Subnet ACL
      Security Group ACL

      We use a special set of AWS security permissions to limit access to only the instances required for running the RCP clusters, when you deploy RCP on the same VPC as your application servers. 

      When you deploy RCP on a different VPC from your application servers or under a different AWS account you control, all the operational aspects of managing RCP are completely isolated from your application.
  • Why should I run Redis Enterprise on Flash?
    • Redis’ Redis on Flash technology enables you to run Redis on high IOPS SSD instances with high throughput and the same sub-millisecond latencies as RAM-based Redis. The economic benefit is dramatic: the cost of cloud instances required to support your database can be slashed by up to 70%, while maintaining the same blazing fast performance.

      As your data grows, and your processing needs increase, you can achieve cost-effective high speed operational and analytic processing with the versatility of Redis and the cost efficiency of Flash memory. If your dataset is larger than 500GB, running Redis in a fully-automated manner with 24/7 expert support over Redis Enterprise is lower in cost than managing your own Redis instances on the cloud.
  • I use another commercial Redis service. Why should I switch to Redis Enterprise?
    • Redis Enterprise is the only Redis service that offers infinite seamless scalability (i.e. Redis cluster is supported seamlessly without the need to change your application or use a special client), true high-availability, stable top performance, and zero management. Redis Enterprise is also the only Redis service that offers Redis on Flash for substantial cloud resource cost savings.

      For a visual picture, consult this table comparing the commercial Redis services.
  • How many Redis databases can I create and manage?
    • The number of Redis databases is unlimited. The limiting factor is the available memory in the cluster, and the number of shards in the subscription. 

      Note the impact of the specific database configuration on the number of shards it consumes. For example:
      -Enabling database replication, without enabling database clustering, creates two shards: a master shard and a replica shard.
      -Enabling database clustering creates as many database shards as you configure.
      -Enabling both database replication and database clustering creates double the number of database shards you configure.
  • What happens when a Redis database fills up?
    • As detailed in the open source Redis FAQ, under “What happens if Redis runs out of memory?”:
      …[You] can use the “maxmemory” option in the config file to put a limit to the memory Redis can use. 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 you are using Redis for caching.

      You can set the maxmemory value of each Redis Enterprise database in the management UI using the Memory limit property, as well as configure an eviction policy by setting it to any of the standard Redis behaviors, without interrupting database operations.
  • Can I keep my data safe and always available?
    • Redis Enterprise offers a comprehensive suite of high-availability provisions, including in-memory replication, persistent storage and backups.
  • What is a shard?
    • A shard is any type of provisioned database instance, such as a master copy, replica copy, database shard that is part of a clustered database, etc.
  • What client can I use to connect to the databases in Redis Enterprise?
  • Can my Redis database grow infinitely?
    • Our proxy-based architecture and dynamic clustering technology were built to make Redis scalable and to support its commands and data types at any dataset size. All you need to do is select a plan that fits your dataset’s size. If you expect your dataset to grow or if it occasionally varies in size, we recommend our Pay-As-You-Go plan, for which we charge according to your actual memory consumption in GB/hr.
  • Why do you recommend mapping my availability zone on AWS?
    • The same AWS availability zone name, when shown in different AWS accounts, does not always refer to the same underlying physical infrastructure.
      The mapping process lets us unambiguously identify your availability zone, so we can serve your Redis data from the same physical zone, minimizing inter-zone latencies.
  • Can I export my Redis data from Redis Cloud?
    • Absolutely! There is no lock-in with Redis Cloud. With a click of a button, you can export your latest Redis database backup file from your cloud storage, FTP, or HTTP server to any Redis server. Free plans do not include this capability.

Billing and Customer Service

  • What are your payment schedule and terms?
    • We charge at the beginning of each calendar month (around the 5th of the month) for the usage during the previous month. Usage is based on the size of the dataset (in GB) and its maximum throughput (in ops/sec). We accept all major credit cards.
  • What is the Redis Ltd.’s Service Level Agreement?
    • Find the Service Level Agreement on our legal page.
  • I am a small Redis user. Why should I switch to Redis Cloud?
    • You are probably using one of those small instances to run your Redis and connect it to a small block storage volume, such as a small AWS EBS volume. These instances and volumes were not built for the typical high-throughputs and low-latencies of Redis’ use cases. You probably also suffer occasionally from the “noisy neighbor” phenomenon, in which other cloud applications share a physical server and storage volume with you, making your Redis performance unstable.

      Redis Cloud runs your dataset on the strongest cloud servers, so even if your dataset size is just a few megabytes, you enjoy the best performance available today. In addition, we automatically isolate “noisy neighbors,” so your Redis performance is never affected. Read here for more info.
  • Are my dataset/setup/endpoints affected if I upgrade or downgrade my subscription?
    • No. Any changes you make to your Redis Cloud subscription are purely administrative. They do not affect service to your application in any way. You can downgrade or upgrade your subscription at any time with no downtime or performance impact.
  • Can I run Redis Cloud on my own servers?
    • Redis Cloud is a fully-managed cloud service currently offered only on public clouds and Platform-as-a-Service (PaaS). Redis Enterprise can be run on your own servers inside AWS VPCs.