whichdb
vs

Datomic vs KurrentDB (EventStoreDB)

Datomic: Immutable Datalog database from Nubank where every fact is timestamped and queries run in the app process. KurrentDB (EventStoreDB): A purpose-built event store for event sourcing, with streams, subscriptions and projections.

key differences

  • Datomic is primarily a relational database; KurrentDB (EventStoreDB) is event store.
  • Licensing: Datomic is open source (permissive) (Apache-2.0 (binaries only; source not published)); KurrentDB (EventStoreDB) is source-available (Kurrent License v1 (KLv1)).
  • Transactions: Datomic offers full ACID; KurrentDB (EventStoreDB) offers limited.
  • Only Datomic has joins, secondary indexes, full-text search.
  • Only KurrentDB (EventStoreDB) has json, pub/sub, encryption at rest, role-based access, streaming ingest.
  • Datomic can run embedded in your application process.

choose datomic for

  • +Financial and banking domain models needing auditability
  • +Systems that must answer what was known at a given time
  • +Complex domain graphs in Clojure services

best at · OLTP, Event sourcing, Ledger

choose kurrentdb for

  • +Event-sourced domain models with CQRS
  • +Audit-heavy financial and logistics systems
  • +Integrating microservices via durable event streams

best at · Event sourcing, OLTP, Pub/Sub

DatomicImmutable Datalog database from Nubank where every fact is timestamped and queries run in the app process.
KurrentDB (EventStoreDB)A purpose-built event store for event sourcing, with streams, subscriptions and projections.
overview
Primary model
Relational
Event Store
Also supports
Graph
–
Type
Database engine
Database engine
Status
Active
Active
Developer
Nubank (Cognitect)
Kurrent, Inc.
First release
2012
2012
Latest version
1.0.7745 (Oct 16, 2026)
26.2.3 (Oct 19, 2026)
License
Open source (permissive)Apache-2.0 (binaries only; source not published)
Source-availableKurrent License v1 (KLv1)
Free tier
✓
✓
popularity
WhichDB Score
14.9
18.6
Rank
#225
#177
GitHub stars
–
5.9K
Stack Overflow questions
436
185
scale & guarantees
Comfortable data size
Medium (≤ 10 TB)
Medium (≤ 10 TB)
Horizontal scaling
None
None
Multi-region
None
Read replicas
ACID
Full
Limited
Consistency
Strong
Strong
Schema
Flexible
Schemaless
Architecture
Distributed, Shared storage
Single node, Distributed, Client server
deployment
Self-hosted
✓
✓
Vendor-managed cloud
—
✓
Serverless
—
—
Embedded
✓
—
Edge
—
—
Clouds
AWS
AWS, Google Cloud, Azure
capabilities
Transactions
✓
✓
Joins
✓
—
Secondary indexes
✓
—
Full-text search
✓
—
Vector search
—
—
Geospatial
—
—
JSON
—
✓
Change data capture
✓
✓
Triggers
—
—
Stored procedures
—
—
Materialized views
—
—
TTL / expiry
—
—
Pub/Sub
—
✓
Columnar storage
—
—
In-memory
—
—
Durable persistence
✓
✓
Compression
—
—
Encryption at rest
—
✓
Role-based access
—
✓
Time travel
✓
✓
Branching
—
—
Online schema changes
—
—
Streaming ingest
—
✓
Offline sync
—
—
Runs in WebAssembly
—
—
interfaces
Query languages
Datalog, Pull API
Stream reads/subscriptions API, JavaScript projections, SQL (Arrow Flight)
Client languages
Clojure, Java
C#, Java, JavaScript, Go, Python, Rust
Best for
OLTP, Event sourcing, Ledger, Knowledge graph
Event sourcing, OLTP, Pub/Sub, Streaming
Add more to this comparisonNot sure either fits? Try smart match

Datomic vs KurrentDB (EventStoreDB): FAQ

What is the difference between Datomic and KurrentDB (EventStoreDB)?

Datomic: Immutable Datalog database from Nubank where every fact is timestamped and queries run in the app process. KurrentDB (EventStoreDB): A purpose-built event store for event sourcing, with streams, subscriptions and projections. Datomic is primarily a relational database; KurrentDB (EventStoreDB) is event store. Licensing: Datomic is open source (permissive) (Apache-2.0 (binaries only; source not published)); KurrentDB (EventStoreDB) is source-available (Kurrent License v1 (KLv1)). Transactions: Datomic offers full ACID; KurrentDB (EventStoreDB) offers limited.

When should I choose Datomic over KurrentDB (EventStoreDB)?

Choose Datomic for financial and banking domain models needing auditability; systems that must answer what was known at a given time; and complex domain graphs in Clojure services. Choose KurrentDB (EventStoreDB) for event-sourced domain models with CQRS; audit-heavy financial and logistics systems; and integrating microservices via durable event streams.

Is Datomic or KurrentDB (EventStoreDB) more popular?

KurrentDB (EventStoreDB) ranks #177 on the WhichDB Score (18.6/100) and Datomic ranks #225 (14.9/100). Popularity is not fit: check the requirements that matter for your project.

Are Datomic and KurrentDB (EventStoreDB) open source?

Yes. Datomic is open source. License: Apache-2.0 (binaries only; source not published). Not in the OSI sense. KurrentDB (EventStoreDB) is source-available: you can read the code, but the license restricts some uses, typically offering it as a competing managed service. License: Kurrent License v1 (KLv1).