Amazon Web Services Introduction to Elastic Cache (original) (raw)

Last Updated : 3 Jun, 2026

Amazon ElastiCache is a fully managed, in-memory caching service supporting flexible, real-time use cases. It allows you to deploy, run, and scale popular open-source compatible in-memory data stores seamlessly within the AWS Cloud.

Stores data in RAM rather than on physical disks, reducing read and write latencies from milliseconds to microseconds.
Supports both Redis OSS (and Valkey) and Memcached engines to work natively with existing application codebases.
Acts as a high-speed data buffer in front of databases like Amazon RDS or DynamoDB to handle read-heavy workloads.
Offers both simple and advanced clustering modes to support high availability and write-scaling.
Provides a serverless deployment option that automatically scales memory and processing capacity based on real-time application demands.

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Amazon ElastiCache architectural positioning between application and database

**Note: Caching is the process of storing frequently accessed data in a temporary, high-speed data storage layer known as a cache.

Redis vs. Memcached

ElastiCache supports two distinct in-memory data store engines:

**Feature	**Redis (Recommended)	**Memcached
**Data Structures	Complex. Strings, Hashes, Lists, Sets, Sorted Sets, Bitmaps, and Geospatial Indices.	Simple. Simple Key-Value store (Strings only).
**Persistence	Yes. Supports snapshots (RDB) and append-only files (AOF) for backup and restore.	No. Purely volatile cache; data is lost on node reboot.
**Replication	Yes. Supports primary-replica replication and Multi-AZ failover.	No. Scaled out horizontally through partitioned nodes.
**Cluster Mode	Yes. Shards data across multiple node groups for high write scalability.	Yes. Multi-threaded architecture natively optimized for vertical multi-core scaling.
**Pub/Sub	Yes. Native support for Publish/Subscribe messaging patterns.	No.
**Best For	Leaderboards, Session Stores, Real-time Analytics, and Priority Queues.	Simple, high-performance database query caching and transient session data.

**Note: Use Redis for 95% of modern workloads. Select Memcached only if you require a simple, multi-threaded cache or need compatibility with a legacy Memcached codebase.

Cluster Mode Enabled vs. Disabled

When designing a Redis cluster, you must choose its operational architecture during creation:

**Feature	**Cluster Mode Disabled	**Cluster Mode Enabled
**Structure	1 Primary + up to 5 Replicas.	Up to 500 Shards (each w/ Primary + Replicas).
**Data Partitioning	None (Single node group holds 100%).	**Sharding (Data spread across node groups).
**Scaling (Read)	Add up to 5 replicas.	Add replicas or shards (Horizontal).
**Scaling (Write)	**Vertical only (Scale up instance type).	**Horizontal (Add more shards).
**Best For	Small datasets; simplest logic.	High write throughput; TB-scale datasets.

Serverless vs. Provisioned

AWS provides two deployment models to manage ElastiCache cluster capacity:

**Feature	**ElastiCache Serverless	**Self-Designed (Provisioned)
**Management	Zero-touch; auto-scales CPU/Memory.	Manual node/instance type selection.
**Scaling Speed	**Instant; no capacity planning needed.	Manual or via Auto-Scaling policies.
**Pricing Model	Data stored (GB-hr) + ECPUs (Compute).	Fixed hourly rate per node.
**Availability	Multi-AZ by default.	User-configured (Single or Multi-AZ).
**Best For	Spiky traffic; new apps; dev/test.	Steady-state traffic; Reserved Node savings.

Caching Strategies

To use ElastiCache effectively, your application must implement an appropriate caching pattern:

Lazy Loading (Cache-Aside)

**Mechanism: The application attempts to read from the cache first. If a cache miss occurs, the application queries the database, writes the retrieved data to the cache, and returns it to the client.
**Pros: Memory is used efficiently since only requested data is cached.
**Cons: The initial request suffers a performance penalty due to the round-trip database query.

Write-Through

**Mechanism: The application writes new or updated data to both the database and the cache simultaneously.
**Pros: Guarantees the cache is always updated, preventing dirty reads.
**Cons: Increases write latency due to completing two consecutive write operations.

Steps to Access Amazon ElastiCache Console

Follow these steps to access the AWS Management Console and locate ElastiCache:

**Step 1: Sign in to the AWS Management Console, type "ElastiCache" in the top search bar, and select the first option.

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Searching for ElastiCache in the AWS Management Console

**Step 2: Use the left navigation pane to configure Redis/Valkey clusters, Memcached clusters, parameter groups, or subnet groups.

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The Amazon ElastiCache service landing page and left navigation panel

ElastiCache vs. DynamoDB DAX

While both are in-memory caching solutions, they differ in flexibility and integration scope:

**Feature	**ElastiCache (Redis)	**DynamoDB DAX
**Purpose	General-purpose cache designed for any database type (e.g., Amazon RDS, Aurora, DynamoDB, MongoDB, or on-premises databases).	Specialized, transparent write-through/read-through cache built exclusively for Amazon DynamoDB.
**Code Changes	Yes. Requires explicitly writing application logic to check the cache, handle misses, and update records.	None. Requires only changing the endpoint in your DynamoDB client configuration.
**Flexibility	High. Can store multi-purpose objects, application sessions, operational queues, and leaderboards.	Low. Caches only API results from DynamoDB GetItem, BatchGetItem, Query, and Scan calls.

Common Use Case Architectures

Implement ElastiCache to resolve performance bottlenecks in the following architectural scenarios:

**Database Query Caching: Position ElastiCache in front of relational databases like Amazon RDS to cache heavy read-queries (e.g., "Daily Top 10 Products"), relieving CPU utilization on RDS.
**Session Management Store: Store volatile customer sessions and shopping carts. Because Redis supports persistence, session data remains secure and accessible even if backend web application servers reboot.
**Real-Time Leaderboards: Utilize native Redis Sorted Sets to maintain instant global rankings for millions of active concurrent users with sub-millisecond retrieval.