Over the past twenty-five years, caching architectures have evolved through three distinct generations:
- Generation 1 (Local In-Memory / Memcached): Simple key-value byte caching on local servers.
- Generation 2 (In-VPC In-Memory Databases / Redis): Centralized clusters with rich data structures, persistence, and pub/sub.
- Generation 3 (Distributed Edge Caching Proxies / ApexCache): Globally distributed reverse proxies with Change Data Capture (CDC) and SingleFlight request coalescing.
Each tool was designed for specific trade-offs. Here is an architectural breakdown of when to use Memcached, when to use Redis, and when to use an Edge Caching Gateway.
1. Memcached: The Raw Multi-Threaded Byte Cache
Memcached was created in 2003 for LiveJournal. It is a multi-threaded, in-memory key-value cache designed to store raw string or binary blobs.
When Memcached Wins:
- Multi-Threaded Throughput: Memcached utilizes multiple CPU cores efficiently on a single large instance (e.g. 64 vCPUs).
- Simplicity: If you only need a raw LRU string cache without persistence, data structures, or replication overhead.
Where Memcached Falls Short:
- No native persistence or replication failovers.
- No rich data structures (lists, sets, sorted sets).
- In-VPC only: Does not reduce network distance for global users.
2. Redis: The In-Memory Data Structure Store
Redis, released in 2009, transformed backend engineering by introducing rich data structures and replication.
When Redis Wins:
- Queues & Background Jobs: BullMQ, Sidekiq, Celery.
- Real-Time Pub/Sub & WebSockets: Managing live event distribution across microservices.
-
Distributed Locks & Counters:
INCRBY,Redlock, atomic rate limiting. -
Geospatial & Leaderboards: Sorted Sets (
ZSET) and Geo commands.
Where Redis Falls Short:
- API Response Caching: Requires extensive custom invalidation code and suffers from dual-write desync.
- Single-Region Latency: Sits in your cloud VPC, adding 150ms–300ms of cellular latency for global mobile users.
3. Edge Caching Gateways (ApexCache): The Global HTTP Proxy
ApexCache sits directly in the HTTP traffic path between client applications and your backend servers.
When Edge Caching Wins:
- Accelerating REST & GraphQL APIs: Drops response times to under 15ms globally without modifying backend application code.
- Automated Database Invalidation: Uses Change Data Capture (CDC) to purge cache tags directly on database commits.
- Thundering Herd Protection: SingleFlight coalesces thousands of concurrent misses into 1 origin query.
Complete Technology Comparison
| Dimension | Memcached | Redis | ApexCache (Edge Proxy) |
|---|---|---|---|
| Primary Role | In-VPC Byte Cache | In-VPC Data Structure Store | Global API Edge Gateway |
| Network Location | Central VPC Subnet | Central VPC Subnet | Globally Distributed Edge PoPs |
| Threading Model | Multi-threaded | Single-threaded event loop | Multi-threaded Lock-Free Native |
| Data Structures | Strings / Blobs only | Strings, Hashes, Lists, Sets, ZSets | Serialized HTTP JSON / GraphQL |
| Invalidation Mechanism | Manual app delete()
|
Manual app DEL
|
Real-Time Database CDC & Webhooks |
| Cache Stampede Guard | None | Manual distributed locks | Native SingleFlight coalescing |
| Integration | Custom client code | Custom client code | 1 DNS CNAME record (Zero code) |
Summary Recommendation
- Use Memcached if you have a legacy, high-concurrency raw byte caching workload inside a single VPC.
- Use Redis for stateful operations: job queues, rate limiters, session storage, and pub/sub.
Use ApexCache in front of your HTTP APIs to handle read traffic, eliminate database stampedes, and deliver sub-15ms response times to global users.
Documentation & Guides: getapexcache.com/docs
