XTDB Core2 aims to become the world's first general-purpose Immutable Database. Ultimately, Core2 will serve hybrid transactional-analytical workloads. Core2 is currently in active R&D with a functioning core.
Star on GitHub Stay NotifiedRead Håkan's slides from his talk: Light and Adaptive Indexing for Immutable Databases.
Try Jeremy's exercises from his workshop: Bitemporal Data Management with XTDB.
Boot Core2 in seconds.
docker pull xtdb/core2
docker run -p 5432:5432 xtdb/core2Use any Postgres-compatible client.
psql -h localhostXTDB does not require any pre-defined schema or tables. Every insert, update, and delete is immutable.
INSERT INTO posts (id, user_id, text)
VALUES (1234, 5678, 'Hello World!');
SELECT posts.text FROM posts;Nested data is natural. Objects are not opaque. Instead, they are seamlessly integrated with SQL.
INSERT INTO people (id, name, friends)
VALUES (5678, 'Sarah',
[{'user': 'Dan'},
{'user': 'Kath'}]);SELECT people.friends[2] FROM people;XTDB defaults to the SQL:2011 standard. It also offers optional defaults for a more intuitive experience.
-- SET APPLICATION_TIME_DEFAULTS TO ISO_STANDARD;
SET APPLICATION_TIME_DEFAULTS TO AS_OF_NOW;Time in XTDB is optional – but universal. Advanced applications can even query time itself.
INSERT INTO posts (id, user_id, text, application_time_start)
VALUES (9012, 5678, 'Happy 2025!', DATE '2025-01-01');
SELECT posts.text FROM posts
FOR APPLICATION_TIME AS OF DATE '2025-01-02';
SELECT posts.text FROM posts;XTDB speaks Apache Arrow as readily as it speaks SQL.
SELECT more_posts.text
FROM ARROW_TABLE('https://xtdb.com/more_posts.arrow')
AS more_posts;To comply with privacy laws, erasure is necessary when handling Immutable Records.
ERASE FROM people WHERE people.id=5678;XTDB Core2's compute nodes can scale independently of its object storage layer. This separation allows immutable records to be retained indefinitely and queries to scale horizontally.
You can find more information at core2docs.xtdb.com, Core2's preliminary documentation.
Core2 is the product of many years' research. If you are a developer or researcher interested in Core2's background, you can read and download our Core2 bibliography on Zotero .
Core2 is not currently stable or intended for real-world evaluation. Please see the rest of the xtdb.com website for information on XTDB 1.x, our commercially-supported software for production use.
To understand the roadmap for Core2 you can follow our GitHub project board. For any other enquiries please contact us to arrange a conversation.
Core2's objective is to take the key principles embodied in XTDB 1.x – immutability, schemaless records, and temporal querying – to a mainstream SQL audience.
| XTDB 1.x | Core2 Research Concept | |
|---|---|---|
| Status | Stable | Experimental (pre-alpha) |
| Initial Stable Release | 2019 | TBD |
| Interface | Java + edn Datalog | SQL — PostgreSQL native drivers, JDBC NewSQL — HTTP (planned), Arrow FlightSQL (planned) |
| Secondary Interface | OpenAPI, Calcite SQL (read-only) | Many secondary languages (Datalog, SPARQL, Gremlin, etc.) are possible |
| Execution Model | Tuple-at-a-Time Sort-Merge Joins | Vectorized Relational Algebra |
| Storage & Compute | Coupled (nodes are full replicas) | Separated (cost-effective scale out) |
| Storage Format | Custom Key-Value encodings | Columnar Apache Arrow |
| Bitemporal Querying | Timeslice only ('as-of') | SQL:2011 and beyond |
| Analytical Querying | No | Yes |
| Temporal Granularity | Milliseconds | Microseconds |
| Index Upgrades | Full log replay | Online |
| Transaction Log | Infinite Retention | Ephemeral WAL |
| Relational Decorrelation | No | Yes |
| Persistence Layer | Transaction Log + Document Store | Object Store |
JUXT holds a fundamental belief that any product we create must be fully open source and XTDB is no exception. We say "fully" because we do not consider "open core" products to be open source. Quality software speaks for itself and does not need to hide behind restrictive licenses.
All software has a lifespan. When closed-source software breathes its last, customers are left stranded. We consider this unethical. Your business should not be forced to accept the risk of closed-source software.
XTDB Core2 is licensed under the GNU Affero General Public License, v3. Commercial and Warranty licenses are available, where required.