Mode 1 — Manual inputs

Use this mode when the user does not have a running Cassandra cluster, or when they prefer to type traffic estimates directly.

If the user mentions a running Cassandra cluster or DataStax deployment, always offer Mode 2 first — diagnostic data produces a more accurate estimate. Fall back to Mode 1 only when diagnostic captures (nodetool tablestats + nodetool info) are unavailable.

Parameters

All positional, in this exact order:

Position	Name	Required	Format	Notes
1	region	yes	AWS region code (e.g. `us-east-1`, `eu-west-1`, `ap-southeast-2`)	Must exist in `assets/data/regions.json`.
2	reads_per_second	yes	integer ≥ 0	Strongly-consistent reads. Halved in output for eventual-consistency pricing.
3	writes_per_second	yes	integer ≥ 0	Single-row inserts/updates. Does not include TTL auto-deletes (column 6).
4	avg_row_size_bytes	yes	integer	Typical 256-4096. Include partition key, clustering key, and all column bytes; exclude internal Cassandra overhead. Default `1024` only when truly unknown.
5	storage_gb	yes	number	Single-replica compressed storage in GB. Keyspaces applies replication internally at RF=3; pass the compressed single-replica figure.
6	ttl_deletes_per_second	no (default `0`)	integer ≥ 0	TTL-expiring writes per second. Priced at the same rate as regular writes (writes are billed; reads/deletes are implicit).
7	pitr_enabled	no (default `false`)	`true` / `false`	Backups/point-in-time-recovery. Adds a per-GB-month surcharge.

Command

cd scripts
npx ts-node --project tsconfig.scripts.json calculate.ts \
  <region> <reads/s> <writes/s> <rowSizeBytes> <storageGB> [ttl/s] [pitr] \
  | tee /tmp/keyspaces-calc.json

Example:

npx ts-node --project tsconfig.scripts.json calculate.ts \
  us-east-1 1000 500 1024 100 0 false | tee /tmp/keyspaces-calc.json

Output shape

{
  "region": { "short": "us-east-1", "long": "US East (N. Virginia)" },
  "inputs": { ... the 7 parameters ... },
  "units_per_operation": { "write": 1, "read": 1, "ttl": 1 },
  "on_demand":               { "reads_strong": …, "reads_eventual": …, "writes": …, "ttl_deletes": …, "storage": …, "backup": …, "total": … },
  "provisioned":             { ... same shape ... },
  "savings_plan_available":  true | false,
  "on_demand_savings_plan":  { ... same shape or null ... },
  "provisioned_savings_plan":{ ... same shape or null ... },
  "report_data":             { datacenters, regions, estimateResults, pricing }
}

Values are monthly US dollars unless otherwise noted.

Units-per-operation

Keyspaces bills by the capacity unit, not the raw row count. One Write Capacity Unit (WCU) covers up to 1 KB written; one Read Capacity Unit (RCU) covers up to 4 KB read (strongly consistent) or 4 KB per 2 RCUs (eventually consistent). Rows larger than the threshold consume more units per operation.

units_per_operation.write — ceil(row_size_bytes / 1024). units_per_operation.read — ceil(row_size_bytes / 4096). units_per_operation.ttl — same as write.

Surface these when explaining why a row size change (for example going from 1024 to 2048 bytes) flips the recommendation between on-demand and provisioned.

Presenting the result

Show the user:

A one-row inputs summary — region, reads/s, writes/s, row size, storage, PITR.
A two-column cost table — On-demand vs Provisioned, with line items for reads, writes, TTL deletes, storage, and backup, totaling at the bottom. Include a Savings Plan row when savings_plan_available is true.
A clear recommendation — whichever mode is cheaper at the user's stated traffic pattern, with a one-line reason tied to the read/write ratio.
A line noting the user may generate a PDF via Step 6 if wanted.

Common follow-ups

"What if I double the writes?" — rerun with the new value; writes are linear in cost for both pricing modes.

"What if I add PITR later?" — rerun with true in position 7; PITR cost scales with storage_gb only.

"Should I use on-demand or provisioned?" — Provisioned wins for steady, predictable traffic (utilization > 18% of peak). On-demand wins for spiky or unknown traffic. The script already applies the breakeven; state the recommendation from the totals, then cite which mode won.

"Can you compare two traffic scenarios?" — run calculate.ts twice to different /tmp/*.json paths, then a single generate-pdf.ts --input A --input B to produce a consolidated PDF (see pdf-reporting.md).

/amazon-keyspaces

referencesmode-1-manual-inputs.md