whichdb
vs

eXtremeDB vs kdb+

eXtremeDB: Embedded in-memory and hybrid database for devices, real-time systems and time-series analytics. kdb+: Column-store time-series engine with the q language, a fixture of capital-markets tick data.

key differences

  • eXtremeDB is primarily a key-value database; kdb+ is time-series.
  • kdb+ is built for larger datasets (≤ 1 PB) than eXtremeDB (≤ 10 TB).
  • Horizontal scaling is native in eXtremeDB and manual in kdb+.
  • Transactions: eXtremeDB offers full ACID; kdb+ offers limited.
  • Only eXtremeDB has transactions, vector search, geospatial, role-based access.
  • Only kdb+ has json, stored procedures, pub/sub, streaming ingest.
  • eXtremeDB can run embedded in your application process.

choose extremedb for

  • +Embedded databases in network equipment
  • +Avionics and defence systems
  • +Industrial controllers and edge gateways
  • +In-process market data analytics

best at · Embedded, Edge, Time-series

choose kdb-plus for

  • +Equities, FX and futures tick capture
  • +Trade surveillance and best-execution analysis
  • +Quant research on historical market data
  • +Real-time risk and P&L

best at · Tick data, Time-series, Real-time analytics

eXtremeDBEmbedded in-memory and hybrid database for devices, real-time systems and time-series analytics.
kdb+Column-store time-series engine with the q language, a fixture of capital-markets tick data.
overview
Primary model
Key-Value
Time-Series
Also supports
Relational, Time-Series, Columnar / OLAP, Vector
Columnar / OLAP, Relational
Type
Embedded library
Database engine
Status
Active
Active
Developer
McObject
KX
First release
2001
2003
Latest version
9.0 (Jul 15, 2026)
KDB-X 5.0.20261015 (Oct 15, 2026)
License
ProprietaryCommercial (per-product licensing)
ProprietaryCommercial; KDB-X Community Edition free with resource limits
Free tier
—
✓
popularity
WhichDB Score
4.0
31.8
Rank
#421
#75
GitHub stars
–
–
Stack Overflow questions
–
2.3K
scale & guarantees
Comfortable data size
Medium (≤ 10 TB)
Large (≤ 1 PB)
Horizontal scaling
Native
Manual
Multi-region
None
None
ACID
Full
Limited
Consistency
Strong
Strong
Schema
Strict
Strict
Architecture
Embedded, In memory, Client server, Distributed
In memory, Single node, Client server
deployment
Self-hosted
✓
✓
Vendor-managed cloud
—
✓
Serverless
—
—
Embedded
✓
—
Edge
✓
—
Clouds
–
AWS
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
SQL (eXtremeSQL), Native C/C++ API
q, qSQL, Python (PyKX)
Client languages
C, C++, Java, Python, C#
Python, Java, C, C#
Best for
Embedded, Edge, Time-series, Tick data
Tick data, Time-series, Real-time analytics, Streaming
Add more to this comparisonNot sure either fits? Try smart match

eXtremeDB vs kdb+: FAQ

What is the difference between eXtremeDB and kdb+?

eXtremeDB: Embedded in-memory and hybrid database for devices, real-time systems and time-series analytics. kdb+: Column-store time-series engine with the q language, a fixture of capital-markets tick data. eXtremeDB is primarily a key-value database; kdb+ is time-series. kdb+ is built for larger datasets (≤ 1 PB) than eXtremeDB (≤ 10 TB). Horizontal scaling is native in eXtremeDB and manual in kdb+.

When should I choose eXtremeDB over kdb+?

Choose eXtremeDB for embedded databases in network equipment; avionics and defence systems; and industrial controllers and edge gateways. Choose kdb+ for equities, FX and futures tick capture; trade surveillance and best-execution analysis; and quant research on historical market data.

Is eXtremeDB or kdb+ more popular?

kdb+ ranks #75 on the WhichDB Score (31.8/100) and eXtremeDB ranks #421 (4.0/100). Popularity is not fit: check the requirements that matter for your project.

Are eXtremeDB and kdb+ open source?

No. eXtremeDB is proprietary, closed-source software. License: Commercial (per-product licensing). No. kdb+ is proprietary, closed-source software. License: Commercial; KDB-X Community Edition free with resource limits.