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Aurora Global Database

What it is

Amazon Aurora Global Database is AWS's cross-region read-replica cluster feature for Amazon Aurora. A "separate read-only Aurora cluster that your data will be replicated to" running in a secondary region, fed by asynchronous replication from the primary- region cluster, so applications in the secondary region read from a topologically-nearby Aurora endpoint rather than paying the cross-region latency of every read. (Source: sources/2024-02-15-planetscale-amazon-aurora-pricing-surprising-costs)

Each participating region "is independently scalable, so understanding the compute requirements for that region and selecting an appropriate instance type can help optimize costs."

Why it shows up on this wiki

Aurora Global Database is the canonical wiki instance of patterns/global-read-replica-cluster — one primary region + N read-only secondary regions, with asynchronous replication in between. The pattern's defining characteristic is its three-layer cost model (per Morrison):

  1. Compute — secondary-region reader instances billed at standard Aurora per-hour rates.
  2. Storage — secondary-region storage billed as a separate Aurora storage SKU.
  3. Replication — "Amazon charges additional fees per 1 million write operations performed, as well as standard data transfer costs to replicate data between regions."

The third layer is what distinguishes Global Database from a single-region Aurora cluster: every write to the primary region becomes a billable event at the replication layer, and the cross-region bytes themselves are charged at AWS's data-transfer rates.

Cost shape summary

  • Primary-region compute + storage — standard Aurora billing.
  • Secondary-region compute + storage — standard Aurora billing, per region.
  • Per-million-writes replication fee — Global Database surcharge.
  • Cross-region data transfer — per-GB bytes billed.

Morrison's framing: Global Database "allows you to have a separate read-only Aurora cluster that your data will be replicated to" — but the per-write fee + transfer cost mean the operator absorbs a replication-cost surface that scales with primary-region write volume, not just with secondary-region read volume.

Contrast with newer Aurora family members

  • Aurora DSQL — multi-region active-active from day one, with consistency guarantees via time-based MVCC. Different trade-off: DSQL writes coordinate across regions, so the cost model isn't per-million-writes to a passive replica.
  • Aurora Limitless — horizontally-scaled within-region Postgres; different scale axis than Global Database's within-cluster cross-region replication.

Aurora Global Database is the read-replica form: primary region owns writes, secondary regions read.

Contrast with PlanetScale read-only regions

Morrison's counter-positioning in the same post: "PlanetScale offers the ability to create read-only regions, where your data is replicated to a selected region that is closer to your application servers in that region. It is very similar to Global database, except you don't need to pay for the data transfer costs, and you still get a full MySQL cluster with the same resources as the selected instance type." Canonical instance of the PlanetScale-bundles-transfer-cost counter-positioning vs Aurora's per-axis billing.

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