whichdb
vs

kdb+ vs QuestDB

kdb+: Column-store time-series engine with the q language, a fixture of capital-markets tick data. QuestDB: Columnar time-series SQL database built for market data and very high ingest rates.

key differences

  • Licensing: kdb+ is proprietary (Commercial; KDB-X Community Edition free with resource limits); QuestDB is open source (permissive) (Apache License 2.0 (open source); Enterprise is commercial).
  • kdb+ is built for larger datasets (≤ 1 PB) than QuestDB (≤ 10 TB).
  • Horizontal scaling is manual in kdb+ and none in QuestDB.
  • Only kdb+ has json, stored procedures, pub/sub, in-memory, encryption at rest.
  • Only QuestDB has materialized views, ttl / expiry, role-based access, online schema changes.

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

choose questdb for

  • +Market data and order book analytics
  • +Trading and risk dashboards
  • +Industrial and aerospace telemetry
  • +Crypto exchange tick storage

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

kdb+Column-store time-series engine with the q language, a fixture of capital-markets tick data.
QuestDBColumnar time-series SQL database built for market data and very high ingest rates.
overview
Primary model
Time-Series
Time-Series
Also supports
Columnar / OLAP, Relational
Columnar / OLAP, Relational
Type
Database engine
Database engine
Status
Active
Active
Developer
KX
QuestDB
First release
2003
2019
Latest version
KDB-X 5.0.20261015 (Oct 15, 2026)
10.1.0 (Oct 22, 2026)
License
ProprietaryCommercial; KDB-X Community Edition free with resource limits
Open source (permissive)Apache License 2.0 (open source); Enterprise is commercial
Free tier
✓
✓
popularity
WhichDB Score
31.8
34.1
Rank
#75
#60
GitHub stars
–
17.5K
Stack Overflow questions
2.3K
282
scale & guarantees
Comfortable data size
Large (≤ 1 PB)
Medium (≤ 10 TB)
Horizontal scaling
Manual
None
Multi-region
None
Read replicas
ACID
Limited
Limited
Consistency
Strong
Strong
Schema
Strict
Flexible
Architecture
In memory, Single node, Client server
Single node, Primary replica, 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
q, qSQL, Python (PyKX)
SQL
Client languages
Python, Java, C, C#
Java, Python, Go, Rust, C, C++, C#, JavaScript
Best for
Tick data, Time-series, Real-time analytics, Streaming
Time-series, Tick data, Real-time analytics, IoT
Add more to this comparisonNot sure either fits? Try smart match

kdb+ vs QuestDB: FAQ

What is the difference between kdb+ and QuestDB?

kdb+: Column-store time-series engine with the q language, a fixture of capital-markets tick data. QuestDB: Columnar time-series SQL database built for market data and very high ingest rates. Licensing: kdb+ is proprietary (Commercial; KDB-X Community Edition free with resource limits); QuestDB is open source (permissive) (Apache License 2.0 (open source); Enterprise is commercial). kdb+ is built for larger datasets (≤ 1 PB) than QuestDB (≤ 10 TB). Horizontal scaling is manual in kdb+ and none in QuestDB.

When should I choose kdb+ over QuestDB?

Choose kdb+ for equities, FX and futures tick capture; trade surveillance and best-execution analysis; and quant research on historical market data. Choose QuestDB for market data and order book analytics; trading and risk dashboards; and industrial and aerospace telemetry.

Is kdb+ or QuestDB more popular?

QuestDB ranks #60 on the WhichDB Score (34.1/100) and kdb+ ranks #75 (31.8/100). Popularity is not fit: check the requirements that matter for your project.

Are kdb+ and QuestDB open source?

No. kdb+ is proprietary, closed-source software. License: Commercial; KDB-X Community Edition free with resource limits. Yes. QuestDB is open source. License: Apache License 2.0 (open source); Enterprise is commercial.