CRDTs

Enabling Collaboration in Decentralized Systems

Zach Glindro

$

Strong consistency

No offline access

Loss of data ownership

Service dependency

Eventual consistency

Replica A Online

• Milk

Replica B Online

• Milk

Replica C Online

• Milk

→

C R D T

C onflict-free

R eplicated

D ata

T ypes

C onflict-free

R eplicated

D ata

T ypes

Strong eventual consistency

Operation-based CRDTs

Alice

• Buy milk

Bob

• Buy milk

Alice

• Buy milk — 8:00 AM

Bob

• Buy milk — Don't forget almond milk

Alice

• Buy milk — 8:00 AM; Don't forget almond milk

Bob

• Buy milk — 8:00 AM; Don't forget almond milk

State-based CRDTs

Alice

• Buy milk

Bob

• Buy milk

Alice

• Buy milk
• Get bread

Bob

• Buy milk
• Wash car

Alice

• Buy milk
• Get bread
• Wash‎ car

Bob

• Buy milk
• Get bread
• Wash car

Examples

cereals-inventory.vercel.app

⎘

Cereals Inventory web app

cereals-inventory.vercel.app/dashboard

⎘

Cereals Inventory web app

C R D T

C onflict-free

R eplicated

D ata

T ypes

• Local-first software
• Strong eventual consistency
• Performance and storage
• Maturity

Thank you!