Products / Remembering / EventSourcingDB

Remembering

EventSourcingDB

Because it's more than just data.

The database built for Event Sourcing. Write, read, and observe events with consistency guarantees and a tamper-evident history – as a single binary, from a Raspberry Pi to Kubernetes.

Download Read the docs

Free up to 25,000 events – in development and in production, no license key needed.

License: Proprietary
Runs on: Container, Linux, macOS, Windows
Speaks: HTTP

Why EventSourcingDB

General-purpose databases can store events. They just don't understand them.

Relational databases, document stores, and streaming platforms all get you part of the way. Ordering, append-only behavior, concurrency, and replay are then up to you. EventSourcingDB takes care of exactly these things – and nothing more.

Events stay in order and are never changed. Append-only is the model, not a convention.
Every write can check its preconditions. Nobody borrows a book that is already gone.
History and live updates are one stream. Replay everything, then keep going in real time.

Our design principles →

POST /api/v2/data/write-events HTTP/1.1
Authorization: Bearer secret
Content-Type: application/json
{
  "events": [{
    "source": "https://library.eventsourcingdb.io",
    "subject": "/books/42",
    "type": "io.eventsourcingdb.library.book-borrowed",
    "data": { "readerId": "17" }
  }],
  "preconditions": [{
    "type": "isSubjectPopulated",
    "payload": { "subject": "/books/42" }
  }]
}

One HTTP call, one CloudEvent, one precondition. If book 42 has never been acquired, the write is rejected.

Capabilities

Sixteen reasons, four promises.

Every capability links to the part of the docs where you can check it for yourself.

Trust

Reliable storage

Atomic writesEvery write is fully committed, or not at all.Consistency Guarantees
Optimistic lockingPreconditions detect concurrent writes without extra roundtrips.Preconditions
SnapshotsFast replays, even with long event streams.Snapshots
Tamper-evident historyEvery event is cryptographically chained to the one before.Verifying Store Integrity

Insights

Answers to all your questions

Hierarchical subjectsGroup related events and read whole branches at once.Subjects
Time travelRecover any historical state and explore what-if scenarios.Reading Events
Replay to liveReplay the past and continue in real time without a gap.Observing Events
Natural-language queriesAsk questions about your events through the MCP server.Introduction to the MCP Server

Compatibility

From Raspberry Pi to the cloud

Temporary dataFull features with data that is removed on shutdown, for fast tests.Running EventSourcingDB
Management UIHealth, license state, and EventQL in the browser.Using the Management UI
One-minute configurationA handful of CLI flags, nothing more.CLI Overview
Runs anywheremacOS, Linux, Windows, on x86 and ARM, in Docker or Kubernetes.Installing EventSourcingDB

Integration

Frictionless integration

Client SDKsOfficial SDKs for eight languages.Client SDKs – Overview
CloudEventsStandard event format, no lock-in.CloudEvents
MonitoringHealth API, Prometheus, and OpenMetrics built in.Logging and Monitoring
Real-time subscriptionsNo extra message broker needed.Observing Events

Accessories

Everything that comes with EventSourcingDB.

Client SDKsNative access from your language.

.NETElixirGoJavaJavaScriptPHPPythonRust

MCP serverConnect EventSourcingDB to an LLM and query your events in natural language.

Claude Code pluginSkills for writing, reading, and querying events, from local development to schemas.

Merkle CLIVerify backups with Merkle proofs.

Comparison

Where EventSourcingDB fits in.

Other tools are great at what they were built for. Here is how they compare when the job is Event Sourcing – from our point of view, as the makers of EventSourcingDB.

	Relational databases	NoSQL databases	Event streaming	EventSourcingDB
Ordered, append-only streams	Custom tables, append-only enforced by hand	Ordering via partitioning schemes or naming conventions	Ordered, but built for propagation, not as a long-term record	Native, with stream separation by subject
Concurrency per write	Ad hoc locking or optimistic concurrency in the application	Generally no consistent concurrency control	No stream-level isolation	Preconditions on every write
Snapshots and replay	Built yourself	Built from scratch	No built-in snapshots	Built in, including replay to live
Operation	Mature, well known	Flexible, scalable	Powerful, but a platform of its own	One binary, an HTTP API, minimal configuration

The full comparison →

Pricing and licensing

Free to start. Licensed per instance.

Every plan includes every feature. What differs is the number of events you store, and who you are.

Free

Evaluation, development, and smaller systems

0 €

up to 25,000 events

In development and in production

No license key needed
All features included
Community support

Download

Commercial

Companies and teams

2,500 €

per instance and year, net

or 750 € per instance and quarter

Unlimited events
All features included
Support plans available

Get a license

Individual developer

Natural persons building in a private capacity

360 €

per instance and year, plus 19 % VAT

or 120 € per instance and quarter

Technically identical to Commercial
Invoice issued to you personally
Not for companies, including one-person companies

Get a license

Volume and OEM

Larger fleets and hardware manufacturers

On request

Terms tailored to your setup

Volume licenses
OEM and embedded use

Contact sales

All prices per instance. For commercial licenses, VAT depends on your country; within the EU, the reverse-charge mechanism may apply with a valid VAT ID. Licenses renew automatically at the end of their term.

Reduced terms

Start-ups, non-profit organizations, schools, universities, research institutions, and similar may qualify for reduced terms on request.

Ask about reduced terms →

Support plans

Optional, on top of any license. One plan covers your organization, billed yearly.

Community-onlyFree

Connect with the community via GitHub.

Basic750 € per year, net

Contact via email, first reply within two business days.

Extended1,500 € per year, net

Contact via email, callback possible, first reply within 24 hours, 7 days a week.

EnterpriseOn request

Support and contact tailored to your business needs, such as 24/7 availability.

No online activationThe license is a file. There are no remote license checks, so EventSourcingDB runs in air-gapped networks, too.

Your data is never lockedWhen a license expires, EventSourcingDB switches to read-only mode. All data stays readable.

Every feature, every planNo editions, no feature gates. The free tier is the full product.

Licensing in detail →

Family

The EventSourcingDB family

Remembering

EventSourcingDB Auditing Services

Early access

EventSourcingDB chains every event to the one before it. Auditing Services checks that chain continuously and hands its fingerprints to an external custodian, so that a change to stored events no longer goes unnoticed – not even one made by whoever runs the database. The events themselves never leave your infrastructure.

Continuous chain verification and external fingerprint custody for EventSourcingDB.

Discover EventSourcingDB Auditing Services →

Analyzing

EventSourcingDB Analysis Services

Early access

Connect it to EventSourcingDB, and it works out for itself what your events contain, proposes the analyses the data supports, and keeps every number live. There is no data model to maintain, no ETL job, and no schema migration.

Live analyses and dashboards, inferred from the events of an EventSourcingDB.

Discover EventSourcingDB Analysis Services →

Get started