Right-size DynamoDB

intermediate

Scenario & brief

A key-value service with steady, predictable traffic (peak ~6,000 rps) runs DynamoDB with hundreds of provisioned capacity units it never uses — and the compute tier is single-AZ.

Targets: p99 ≤ 180 ms, 99.95% availability, critical durability, under $400/mo.

DynamoDB is inherently multi-AZ and durable, so the data tier's availability is handled — the lever is capacity. For steady load, provisioned capacity is cheaper than on-demand, but only if you size it to actual demand rather than the sky. Right-size the units and fix the compute tier's AZ spread.

6,000 rps peakp99 ≤ 180ms99.95% availdurability: criticalbudget $400/mo

App Servers

Compute

Instance class

Scaling

Instances (static)

3instances

Availability Zones

Purchasing

System health

Erupting · SLA breach

/ 100

Score

SLA not met yet

Monthly cost

$982

Budget $400/mo · $582 over

Metrics

Capacity90

Availability50

Durability100

Cost efficiency0

Requirements

Peak capacity — 5400 rps compute · 72000 rps db (need ≥ 6000 rps)
p99 latency — ~134 ms (need ≤ 180 ms)
Availability — 99.50% (need ≥ 99.95%)
Durability — protected (need redundancy + backups)
Budget — $982/mo (need ≤ $400/mo)

Advisor

Compute tops out at ~5400 rps but peak demand is 6000 rps — requests will queue.
Compute runs in a single AZ — spread across ≥2 AZs (with ≥2 instances) to meet the availability target.

Discussion

No comments yet. Be the first to start the discussion.

For learning purposes only. Costs and capacities are illustrative, not live AWS prices. Not affiliated with or endorsed by Amazon Web Services.