Our ElastiCache bill was $5,081/month. We thought it was $1,883. The hidden costs were killing us.
The Real Cost of Redis
Everyone knows the instance cost. Nobody measures the full picture:
| Cost | Visible? | Monthly |
|---|---|---|
| Instance hours (3x r7g.xlarge) | Yes | $1,883 |
| Cross-AZ data transfer | Hidden | $847 |
| Serialization CPU overhead | Hidden | $1,200 |
| Engineering time (cluster ops) | Hidden | $1,151 |
| Total | $5,081 |
The serialization tax is the worst. Every GET serializes the value to RESP protocol, transfers it over TCP, and deserializes on the client. At 64-byte session tokens, this is negligible. At 4KB values (ML embeddings, PQ keys, API responses), it dominates latency.
The Fix: Add an L1 Tier
Instead of replacing Redis, we added an in-process L1 cache in front of it:
L1 handles 95% of reads. Redis handles the remaining 5% (cache misses + shared state). Database handles cold data.
The Results
| Metric | Before | After |
|---|---|---|
| Redis cluster size | 3 nodes | 1 node |
| Monthly cost | $5,081 | $1,248 |
| P50 latency | 0.31ms | 0.000031ms |
| P99 latency | 1.2ms | 0.12ms |
| Hit rate | 68% (Redis LRU) | 99.2% (CacheeLFU) |
75% cost reduction. 10x P99 improvement. One architectural change.
What Stays in Redis
Redis isn't bad — it's expensive for hot reads. Keep it for:
- Pub/sub (real-time notifications)
- Shared mutable state (counters, locks)
- Persistence (RDB/AOF backup)
- Replication (cross-region consistency)
Move hot reads to L1. Keep Redis as L2. That's the architecture.
How
Cachee initialized at /Users/ericbeans/.cachee
Config : /Users/ericbeans/.cachee/config.toml
Port : 6380
Max keys : 1000000
TTL : 3600s
L0 tier : enabled (64 shards)
Attest : disabled (enable with cachee attest enable)
Verify : trust_cached (1% probabilistic sample)
Strict FP : disabled
Key ID : 51630c2cc2e72565645475c764964380
Plan : Free (10M ops/month)
Start with: cachee start
Upgrade: cachee plan upgrade
Point your Redis client at localhost:6380. Cachee falls through to your existing Redis on miss. Zero code changes.
Full breakdown: Reduce Redis Costs: The Hidden Tax on Every Request
More: ElastiCache Cost Playbook | Cachee vs Redis Comparison | Install