aws_qldb_ledger cost estimation

An aws_qldb_ledger is a fully-managed ledger database with an immutable, cryptographically-verifiable transaction journal — built for systems of record (financial transactions, supply chain, registrations) where you need a provable history. It's serverless: cost is usage across write IOs (~$0.70 per million), read IOs (~$0.136 per million), journal storage, and indexed storage (~$0.25/GB-month). 10M write IOs plus 20 GB of indexed storage is ~$12/month.

Because every change appends to the immutable journal, write IOs and journal storage grow monotonically — the history is never overwritten. That's the point of a ledger, but it means storage accrues over the ledger's life, and write-heavy workloads accumulate IO and journal cost steadily.

Note that AWS has announced end of support for Amazon QLDB; new systems-of-record workloads are steered toward alternatives (e.g. a verifiable ledger built on a relational database). For existing ledgers, the cost levers are reducing unnecessary writes and pruning/exporting old journal data where the use case allows.

c3x prices the ledger from monthly write-IO and storage volumes; reads are usage-driven.

Terraform example

A minimal but realistic configuration that C3X can estimate.

resource "aws_qldb_ledger" "records" {
  name             = "system-of-record"
  permissions_mode = "STANDARD"

  tags = {
    Purpose = "audit-ledger"
  }
}

Pricing dimensions

What you actually pay for when you provision aws_qldb_ledger.

Dimension	Unit	What's being charged
Write IOs	per 1M IOs	Per million write IOs appended to the immutable journal. $0.70 per 1M write IOs → 10M = $7/month
Indexed storage	per GB-month	Indexed (current state) storage; journal storage bills separately and grows monotonically. $0.25/GB-month → 20 GB = $5/month
Read IOs	per 1M IOs	Per million read IOs for queries against the ledger. Usage-based.

Sample C3X output

10M write IOs/month + 20 GB indexed storage:

aws_qldb_ledger.records
├─ Write IOs (10M)        10 × 1M-IOs     $7.00
└─ Indexed storage        20 GB-month     $5.00
                          Monthly        $12.00

Optimization tips

Common ways to reduce aws_qldb_ledger cost without changing the workload.

Plan migration off QLDB

Avoids a deprecated-service dead end

AWS has announced end of support for Amazon QLDB. New systems-of-record workloads are steered toward alternatives (e.g. a verifiable ledger on Aurora/PostgreSQL). Plan migration for existing ledgers; that's the strategic cost decision here.

Reduce unnecessary writes

Proportional to writes avoided

Every write appends to the immutable journal, billing write IOs and growing journal storage permanently. Batch and minimize writes — don't write transient or derived data to the ledger that doesn't need an immutable record.

Index only what you query

Per GB-month and write IO reduced

Indexed storage bills per GB-month. Index the fields you actually query against; unnecessary indexes add storage and write IO cost.

Export and archive cold history

Journal storage vs S3 archive rate

QLDB can export journal data to S3. For ledgers where old history is rarely queried, exporting and archiving to cheap S3 storage (within your compliance rules) controls long-term storage growth.

FAQ

How is Amazon QLDB billed?

By usage, with no instances: write IOs (~$0.70/million), read IOs (~$0.136/million), and storage (journal plus indexed at ~$0.25/GB-month). 10M write IOs + 20 GB indexed is ~$12/month. Because the journal is immutable, write IOs and journal storage grow monotonically.

Should I still use QLDB?

AWS has announced end of support for QLDB, so new systems-of-record workloads should use alternatives like a verifiable ledger built on Aurora/PostgreSQL. Existing ledgers should plan migration — that's the key decision beyond runtime cost.

How does c3x estimate the cost?

From monthly write-IO and storage volumes in c3x-usage.yml. Reads are usage-driven; it's a serverless ledger, so there's no instance to price.

Related resources

AWS

aws_rds_cluster

Aurora — a common base for building a verifiable ledger post-QLDB

`aws_qldb_ledger` cost estimation