Why Use Caching?

Imagine an online gaming leaderboard or an e-commerce site's product catalog page — these are read-heavy workloads where data is often requested multiple times within seconds. Instead of querying the database each time, which could be expensive and slow under heavy load, caching allows the application to:

• Serve data directly from memory, reducing latency from milliseconds to microseconds;
• Lower the database load, freeing it up for write operations and less frequent queries;
• Improve overall scalability and reduce infrastructure costs.

Amazon ElastiCache: Features and Use Cases

Amazon ElastiCache supports two open-source caching engines:

Redis

• Advanced data structures: supports strings, hashes, lists, sets, sorted sets, bitmaps, hyperloglogs, and geospatial indexes — enabling complex caching patterns;
• Persistence: options for snapshotting and append-only files, so data can survive node restarts;
• Pub/Sub messaging: allows real-time messaging patterns;
• Atomic operations and scripting: with Lua scripts for complex cache logic;
• TTL support: automatic expiration of keys for cache invalidation.

Use Case Example: a social media app caching user session data, timelines, and real-time notifications benefits from Redis' rich data types and pub/sub features.

Memcached

• Simpler key-value cache;
• Designed for horizontal scaling by adding or removing nodes easily;
• Great for caching arbitrary objects, such as API responses or computed data.

Use Case Example: an e-commerce site caching product detail pages or computed price lists where cache logic is straightforward and scalability is critical.

ElastiCache Architecture & Security

ElastiCache runs inside a dedicated VPC, providing network isolation. It supports:

• Encryption in transit and at rest — securing sensitive cached data;
• Automatic failover and multi-node clusters — ensuring high availability and durability;
• Multi-AZ deployments for Redis — reducing downtime during maintenance or failures.

DynamoDB Accelerator (DAX): Seamless Caching for DynamoDB

DAX is a fully managed, write-through and read-through cache designed specifically for DynamoDB. It provides:

• Automatic caching: no need to manually implement cache keys or expiry;
• Minimal code changes: integrate with existing AWS SDK calls for DynamoDB;
• Sub-millisecond read latency: ideal for latency-sensitive workloads;
• Write-through behavior: all writes go directly to DynamoDB, maintaining strong consistency;
• Clustered architecture with fault tolerance: nodes replicate data for durability and availability.

Use Case Example: a gaming leaderboard app built on DynamoDB benefits greatly from DAX by accelerating frequent read queries without rewriting database access code.

Choosing Between ElastiCache and DAX

Best Practices for Caching

• Set appropriate TTL values: сache only as long as data remains valid. For example, product catalog data might be cached for hours, while user session data might have minutes or seconds TTL;
• Monitor cache metrics: use CloudWatch to track cache hit ratio (percentage of requests served from cache) versus misses (falling back to the database). A low hit ratio may indicate cache inefficiencies or improper TTL settings;
• Secure your cache: run caches in private VPCs, enable encryption in transit and at rest, and use IAM policies to restrict access;
• Cache warming: for DAX and ElastiCache, preload frequently used data after restarts or deployments to avoid latency spikes on first access;
• Avoid cache stampede: when many clients simultaneously request data not yet cached, it can overwhelm your backend. Techniques like request coalescing or distributed locks help mitigate this.

Summary

Caching is an essential technique to drastically reduce read latency and scale applications efficiently. Amazon ElastiCache offers flexible, powerful caching engines for general use cases, while DynamoDB Accelerator (DAX) provides a seamless, zero-code caching layer tailored for DynamoDB workloads. Proper cache design and monitoring ensure that your application remains fast, reliable, and cost-effective.