Announcing 99.99% Availability with Amazon ElastiCache for Redis and Amazon MemoryDB for Redis | Amazon IXD – VGT2 Las Vegas

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Date: February 16, 2023

Location: Amazon IXD – VGT2, 6401 E Howdy Wells Ave, Las Vegas, NV 89115

In the modern cloud landscape, a managed service alleviates the burdens associated with infrastructure management while providing numerous advantages such as scalability, cost efficiency, and enhanced security. These attributes make cloud migration particularly attractive for mission-critical applications. High availability is crucial for these applications, as any downtime can lead to significant revenue losses, hinder team productivity, and diminish customer satisfaction. Recently, Amazon ElastiCache for Redis and Amazon MemoryDB for Redis have introduced an enhanced Service Level Agreement (SLA) guaranteeing 99.99% availability for Multi-Availability Zone (Multi-AZ) configurations.

Previously, these services provided a 99.9% SLA for Multi-AZ setups. The new SLA reflects AWS’s commitment to delivering superior availability compared to the public SLA. Over the past year, AWS has unveiled various innovations in high-availability technology for ElastiCache and MemoryDB, including sophisticated monitoring, faster failover times during primary node failures, and streamlined recovery processes. Thanks to these advancements, we are proud to offer a 99.99% SLA for Amazon ElastiCache for Redis and MemoryDB Multi-AZ configurations. The availability tiers for these services are detailed in the table below. For further information, please review the ElastiCache SLA and MemoryDB SLA.

Every minute of downtime directly affects an application’s ability to process incoming requests, making maximum availability essential for a quality user experience. Workloads that depend on real-time data access, involve massive data volumes, or have strict uptime criteria greatly benefit from highly available in-memory databases. Okta, a prominent identity and access management firm based in San Francisco, shared their perspective on the new 99.99% availability: “Over 17,000 organizations rely on Okta to safeguard their customers’ and workforces’ identities. Delivering a mission-critical service necessitates integrating stability and resilience into every layer of our infrastructure. AWS services like ElastiCache, which inherently provide a 99.99% availability SLA, help us simplify complexities and fulfill our commitments to customers.” – Cassio Sampaio, Senior Vice President of Product at Okta.

This updated SLA is available for the latest versions of ElastiCache for Redis and MemoryDB across all regions where these services are generally accessible. In this post, we will guide you on how to activate the 99.99% availability SLA for ElastiCache and MemoryDB.

Maximizing Availability with ElastiCache for Redis

Activating the Multi-AZ option significantly boosts the fault tolerance and availability of your cluster. With Multi-AZ enabled, ElastiCache for Redis positions the primary and at least one replica node of each cluster shard across different Availability Zones. Should a primary node fail, ElastiCache will automatically promote the read replica with the least replication lag to become the new primary node in just a few seconds. The service then self-corrects the impaired primary or substitutes it with a new replica node while synchronizing data from the new primary. For further insights, refer to our blog post on failure scenarios with Multi-AZ responses here.

ElastiCache for Redis Multi-AZ clusters created after January 13, 2023, and running version 6.2 or later are automatically eligible for the updated 99.99% SLA. If your clusters were established before this date, you can apply a recent engine service update to ensure SLA eligibility.

In the following sections, we will illustrate how to confirm that your ElastiCache for Redis clusters meet the criteria for the 99.99% SLA using both the console and the AWS CLI.

Confirming Eligibility via the Console

To check if your ElastiCache for Redis clusters qualify for the 99.99% SLA using the console, follow the steps below.

1. Ensure Multi-AZ is Enabled
   You can verify that Multi-AZ is active on your ElastiCache clusters in two ways:
   • Through the AWS Trusted Advisor console
   • Through the ElastiCache console

   Using AWS Trusted Advisor Console
   If you manage several ElastiCache for Redis clusters, the simplest method to check if Multi-AZ is inactive is to log into the AWS Trusted Advisor console and review the fault tolerance checks. A green status indicates that Multi-AZ is active, while a yellow status means it’s inactive. Keep in mind that the AWS Trusted Advisor fault tolerance checks require 24 hours to accurately reflect Multi-AZ status. Additionally, these checks are available to customers on Business, Enterprise On-Ramp, or Enterprise support plans. For more details, refer to AWS support plans.

   Using the ElastiCache Console
   You can also verify Multi-AZ status in the ElastiCache console by following these steps:

   • In the ElastiCache console, select Redis Clusters from the navigation pane.
   • Under the Resources tab, select the individual cluster to view its details.
   • In the Cluster details section, check if Multi-AZ is enabled.

   If Multi-AZ is not enabled, ensure that a primary and replica set in each shard is deployed in at least two separate Availability Zones before enabling Multi-AZ. Then, modify your cluster to enable Multi-AZ. For further guidance on this process, refer to the Using the AWS Management Console section of Modifying an ElastiCache cluster.

2. Check that ElastiCache for Redis Clusters are Running Version 6.2 or Later
   On the same Redis clusters page in the ElastiCache console, you can verify if the applicable clusters are running on ElastiCache for Redis version 6.2 or later under Engine version. If the engine version is below 6.2, you can upgrade to a newer version by modifying the cluster. For more information, refer to the Using the AWS Management Console section of Modifying an ElastiCache cluster.
3. Verify that the Latest Engine Service Update is Installed
   If you created an ElastiCache for Redis cluster running version 6.2 or later, or upgraded an existing cluster to version 6.2 or later after January 13, 2023, you can skip this step. To check if your clusters are running the latest engine service update released after January 13, 2023:
   • Select an applicable cluster on the Redis Clusters page.
   • Click on Service updates in the navigation pane to see any applicable service updates for that cluster. You can filter by the release date to find the latest engine service update after January 13, 2023.

   If the console displays a list of service updates, select the engine service update released after January 13th, and choose Apply now.

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