Redis is a fast, in-memory, NoSQL data store that provides sub-millisecond latency. It's often used as a cache to offload primary database systems, but it's also suitable for chat applications, message queues, and real-time analytics.

With Stacktape, you can deploy a fully managed Redis cluster without worrying about capacity scaling, hardware provisioning, cluster setup, patching, or backups. The service is compatible with open-source Redis, so you can use your existing Redis clients.

Under the hood, Stacktape uses Amazon ElastiCache for Redis.

When to use it

Redis is an excellent choice when performance is critical.

Advantages

• Performance: As an in-memory data store, Redis can deliver sub-millisecond response times, making it an order of magnitude faster than disk-based databases.
• Fully managed: Stacktape handles all the operational overhead, including scaling, provisioning, patching, and backups.
• High availability: Supports both clustered and non-clustered modes and provides automatic failover with minimal impact.

Disadvantages

• Data persistence: While Redis offers persistence options like snapshotting and append-only files, it's not as durable as a transactional database with full logging and point-in-time recovery.
• Memory limitations: All of your data must fit in memory.
• Client complexity: Clients connecting to a Redis cluster need to be aware of the cluster's topology, which can require additional configuration.

Basic usage

This example shows a simple, single-node Redis cluster. The only required properties are instanceSize and defaultUserPassword.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')

  myFunction:
    type: function
    properties:
      packaging:
        type: stacktape-lambda-buildpack
        properties:
          entryfilePath: path/to/my/lambda.ts
      joinDefaultVpc: true
      connectTo:
        - myRedisCluster

import { Redis } from 'ioredis';

const redisClient = new Redis(process.env.STP_MY_REDIS_CLUSTER_CONNECTION_STRING);

const handler = async (event, context) => {
  await redisClient.set('currentTime', `${Date.now()}`);

  const value = await redisClient.get('currentTime');

  return { result: value };
};

export default handler;

Instance size

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')

Default user password

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')

Cluster topology

The topology of your cluster, determined by the number of replica nodes and shards, affects its performance and availability.

Single-node cluster

A single-node cluster has only one node and is not highly available.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')

Multi-node cluster

You can add replica nodes to a non-sharded cluster to improve read performance and availability.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')
      numReplicaNodes: 2

Sharded cluster

For horizontally scaled performance, you can enable sharding to distribute data across multiple primary nodes.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')
      enableSharding: true
      numShards: 2
      numReplicaNodes: 2

import { Cluster } from 'ioredis';

const redisClusterClient = new Cluster(
  [
    {
      host: process.env.REDIS_HOST,
      port: Number(process.env.REDIS_PORT)
    }
  ],
  {
    redisOptions: { tls: {}, password: process.env.REDIS_PASSWORD },
    dnsLookup: (address, callback) => callback(null, address)
  }
);

const handler = async (event, context) => {
  await redisClusterClient.set('currentTime', `${Date.now()}`);

  const value = await redisClusterClient.get('currentTime');

  return { result: value };
};

export default handler;

Logging

You can enable logging to send the Redis slow log to a CloudWatch log group.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')
      logging:
        format: json

Forwarding logs

You can forward logs to third-party services. See Forwarding Logs for more information.

Accessibility

You can configure which resources can access your cluster. Redis clusters don't support public IP addresses, so only two access modes are available.

VPC mode

The cluster is only accessible from resources within the default VPC. This includes any function, batch job, or container workload in your stack.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')
      accessibility:
        accessibilityMode: vpc

Scoped VPC mode

This mode is more restrictive. In addition to being in the same VPC, a resource must explicitly list the cluster in its connectTo property to gain access.

resources:
  myRedisCluster:
    type: redis-cluster
    properties:
      instanceSize: cache.t3.micro
      defaultUserPassword: $Secret('redis.password')
      accessibility:
        accessibilityMode: scoping-workloads-in-vpc

Referenceable parameters

Pricing

You are charged for:

• Nodes: The price depends on the instance size, number of shards, and number of replica nodes.
  • Formula: num_shards * (num_replica_nodes + 1) * price_per_node
  • Example 1 (cheapest): A single-node cache.t3.micro cluster costs $0.017/hour (~$12.50/month).
  • Example 2 (sharded): A two-shard cache.t3.micro cluster with one replica per shard costs $0.068/hour (~$49/month).
• Data transfer: Usually no additional cost.
• Backups: Free for the first day of retention, then $0.085/GB per month.

Free Tier (first 12 months)

• 750 hours of t2.micro or t3.micro instances per month.

To learn more, see the AWS pricing page.

API Reference