About in-transit encryption

This page gives an overview of in-transit encryption for Memorystore for Redis.

For instructions how to encrypt a connection with in-transit encryption, see Enabling in-transit encryption.

Memorystore for Redis only supports TLS protocol versions 1.2 or higher.


Memorystore for Redis supports encrypting all Redis traffic using the Transport Layer Security (TLS) protocol. When in-transit encryption is enabled Redis clients communicate exclusively across a secure port connection. Redis clients that are not configured for TLS will be blocked. If you choose to enable in-transit encryption you are responsible for ensuring that your Redis client is capable of using the TLS protocol.

In-transit encryption prerequisites

In order to use in-transit encryption with Memorystore for Redis, you need:

  1. A Redis client that supports TLS or a third-party TLS sidecar
  2. A Certificate Authority installed on the client machine accessing your Redis instance

Native TLS was not supported prior to open source Redis version 6.0. As a result, not every Redis client library supports TLS. If you are using a client that does not support TLS, we recommend using the Stunnel third-party plugin that enables TLS for your client. See Securely connecting to a Redis instance using Stunnel and telnet for an example of how to connect to a Redis instance with Stunnel.

Certificate Authority

A Redis instance that uses in-transit encryption has one or more unique Certificate Authorities (CA) that are used to verify the identity of the server. A CA is a string that you must download and install on the client accessing your Redis instance. A CA is valid for ten years from the date it is created. In order to ensure service continuity, the new CA must be installed on clients of the Redis instance before the previous CA expires.

Certificate Authority rotation

A CA is valid for 10 years upon instance creation. In addition, a new CA becomes available five years after instance creation.

The old CA is valid until its expiration date. This gives you a five year window in which to download and install the new CA to clients connecting to the Redis instance. After the old CA expires you can uninstall it from clients.

For instructions on rotating the CA, see Managing Certificate Authority rotation.

Server certificate rotation

Server-side certificate rotation occurs every 180 days causing a transient connection drop of a few seconds. You should have retry logic with exponential backoff in place in order to reestablish the connection. Certificate rotation does not cause a failover for Standard Tier instances.

Connection limits for in-transit encryption

Enabling in-transit encryption on your Redis instance introduces limits on the maximum number of client connections your instance can have. The limit is dependent on your instance size. You should consider increasing the size of your Redis instance if you need more connections than what is supported by your current capacity tier.

Capacity tier Maximum number of connections for Redis versions 4.0, 5.0, and 6.x1 Maximum number of connections for Redis version 7.0 and later1
M1 (1-4GB) 1000 65,000
M2 (5-10GB) 2,500 65,000
M3 (11-35GB) 15,000 65,000
M4 (36-100GB) 30,000 65,000
M5 (101+GB) 65,000 65,000

1 These connection limits are approximate, and depend on the rate and complexity of Redis commands sent per connection.

Monitoring connections

Since Redis instances with in-transit encryption have specific connection limits, you should monitor the redis.googleapis.com/clients/connected metric to make sure you don't exceed the connection limit. If the limit is surpassed, the Redis instance rejects newly attempted connections. In this circumstance we recommend scaling up your instance to the size that accommodates the required number of connections. If you suspect that idle connections make up a significant number of your connections, you can proactively terminate these connections with the timeout configuration parameter.

Performance impact of enabling in-transit encryption

The in-transit encryption feature encrypts and decrypts data, which comes with processing overhead. As a result, enabling in-transit encryption can reduce performance. Also, when using in-transit encryption, each additional connection comes with as associated resource cost. To determine the latency associated with using in-transit encryption, compare application performance by benchmarking application performance with both a Redis instance that has in-transit encryption enabled and a Redis instance that has it disabled.

Guidelines for improving performance

  • Decrease the number of client connections when possible. Establish and reuse long-running connections rather than creating on-demand short-lived connections.
  • Increase the size of your Memorystore instance (M4 or larger is recommended).
  • Increase the CPU resources of the Memorystore client host machine. Client machines with a higher CPU count yields better performance. If using a Compute Engine VM, we recommend compute optimized instances.
  • Decrease the payload size associated with application traffic because larger payloads require more round trips.

In-transit encryption impact on memory usage

Enabling in-transit encryption reserves some of your Redis instance memory for the feature. All other things being equal, with in-transit encryption enabled, the value for the System Memory Usage Ratio metric is higher because of the additional overhead memory used by the feature.

Redis version 7.0 performance improvements

Using Redis version 7.0 on Memorystore for Redis improves the performance of in-transit encryption. To take advantage of these performance improvements, consider upgrading your instance to use Redis version 7.0.

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