Sequential consistency without borders: how D1 implements global read replication

Read replication of D1 databases is in public beta!

D1 read replication makes read-only copies of your database available in multiple regions across Cloudflare’s network.  For busy, read-heavy applications like e-commerce websites, content management tools, and mobile apps:

• D1 read replication lowers average latency by routing user requests to read replicas in nearby regions.

• D1 read replication increases overall throughput by offloading read queries to read replicas, allowing the primary database to handle more write queries.

The main copy of your database is called the primary database and the read-only copies are called read replicas.  When you enable replication for a D1 database, the D1 service automatically creates and maintains read replicas of your primary database.  As your users make requests, D1 routes those requests to an appropriate copy of the database (either the primary or a replica) based on performance heuristics, the type of queries made in those requests, and the query consistency needs as expressed by your application.

All of this global replica creation and request routing is handled by Cloudflare at no additional cost.

To take advantage of read replication, your Worker needs to use the new D1 Sessions API. Click the button below Continue reading