Strong Consistency

When you create a Document, Key-Value, or Graph Edge collection, you can select the Strong consistency checkbox or set to make it strongly consistent.

Strong consistency aims to resolve data integrity issues like the double-spending problem by ensuring that concurrent read and write operations occur in a linear sequence globally.

How It Works

In Macrometa, collections are used to store a set of JSON documents. Each collection is stored on all the fabric clusters where the collection is located.

Each fabric in Macrometa spans a set of clusters (also called regions or data centers). When a fabric is created, a “spot region” is assigned to it automatically. When you write data to a strongly consistent collection, all write operations are routed internally to the fabric's spot region, which is the collection's "source of truth". This process might result in slightly higher latency due to the internal routing.

Enable Strong Consistency

To enable strong consistency on a collection:

• If using the web console, then select the Strong consistency checkbox when creating a new collection.
• If using the API, then set the strongConsistency boolean flag to true in the POST request body to create a collection.

This setting cannot be changed after the collection has been created.

Read and Write Options

Using the Macrometa API, you can send requests with strong consistency guarantees to collections with strong consistency enabled.

Each read or write request for key-value, document, or edge collections can optionally include the strongConsistency boolean flag in the URL query. This determines where read operations for a strongly consistent collection are performed:

• Without Flag: Reads occur in the local region.
• With Flag: Reads are redirected to the spot region.

Summary Table

This table summarizes how operations are handled based on the collection's consistency setting:

Collection Consistency	Strong Consistency	Causal Consistency
Strong I/O Behavior	Spot read, spot write	Invalid request
Causal I/O Behavior	Local read, spot write	Local read, local write