# kdb+

The tick database trading desks have run for 25 years, queried in q rather than SQL.

*https://stockmarketstack.com/tools/kdb · Tick Data Storage & Time-Series Databases*

## Facts

### At a glance

| Field | Value |
| --- | --- |
| Vendor | KX |
| Category | Tick Data Storage & Time-Series Databases |
| Job | tick_storage |
| Website | https://kx.com/products/kdb/ |
| Pricing model | subscription |
| Free tier | true |
| Open source | false |
| Licence | none |
| Self-hosted | true |
| Tested hands-on | false |
| Last updated | 2026-09-13 |

### Pricing

| Tier | USD | Period |
| --- | --- | --- |
| KDB-X Community Edition | 0 USD | month |
| KDB-X 32 GiB | 1822.92 USD | month |
| KDB-X 64 GiB | 5468.25 USD | month |
| 128 GiB and above | on request | month |

### Coverage

| Field | Value |
| --- | --- |
| Asset classes | none |
| Markets | none |
| Works outside the US | false |
| Data latency | none |
| Platforms | cli, library |
| AI features | none |

### Interfaces

| Field | Value |
| --- | --- |
| API | true |
| Webhooks | false |
| Scripting | q |
| Python | true |
| Spreadsheet add-in | false |
| MCP server | true |
| Export | csv, json, parquet, api |

### Capabilities

Yes: none

No: charting, screening, scanning, backtesting, automation, live_trading, paper_trading, portfolio_tracking, broker_import, tax_reporting, alerts, news, options_analysis

*Verified: pricing 2026-09-13; capabilities 2026-09-13; coverage 2026-09-13.*

## What it is

kdb+ is a column-store database and the interpreter for q, the array language it is queried in.
It is the incumbent on trading desks — the thing a tick-capture system is built out of when the
requirement is millions of messages a second into memory and years of ticks on disk.

The shape a desk builds is standard enough that KX documents it as a reference architecture: a
feed handler, a tickerplant that logs every message and publishes to subscribers, a real-time
database holding today in memory, a historical database holding prior days on disk partitioned by
date, and a gateway routing each query to whichever owns the rows. Tables are splayed column by
column, so a query for one symbol on one day reads the columns it names and nothing else. The
operation that justifies all of it is `aj`, the as-of join lining each trade up with the quote
prevailing at its timestamp — what every TCA and slippage calculation is built on, and what is
painful to express in SQL.

Since 17 November 2025 KX ships the engine as **KDB-X**, currently 5.0 (build 2026-07-23) — the
same engine with a module system around it, not a replacement. Two adjacent KX products are not
this one and are priced separately: kdb Insights, the enterprise platform, and KDB.AI, a vector
database.

## Pricing

The free tier is real and it is new. KDB-X Community Edition costs nothing, has no expiry and
permits commercial use — which the old kdb+ Personal Edition did not. The ceiling is hard: 16GB
of RAM for q, one instance, 4 secondary threads, 16 connections per process, 24 CPU cores in
total. Staging data through GPU workflows to dodge the memory cap is explicitly forbidden, as is
installing it on a server already covered by commercial support.

Above that, KX publishes a price list by memory — $1,822.92 a month at 32 GiB, $5,468.25 at 64
GiB, $11,437.50 at 127 GiB, Contact Sales from 128 GiB. The kdb+ product page carries no price at
all, and a classic commercial licence is still a quote.

## Data & coverage

None. kdb+ ships no market data of any kind — it is where you put data you have already bought or
captured. A TAQ module exists for loading NYSE's files; the files are not included.

## Integrations

PyKX gives Python a first-class interface, and KX publishes an MCP server under Apache 2.0.
Modules cover Parquet, S3-compatible object storage, a REST server and a Postgres wire endpoint,
so a BI tool can connect without speaking q; the SQL module translates a subset of ANSI SQL into q
at runtime. KDB-X runs on Linux (x86 and ARM) and macOS — native Windows is not supported, only
WSL.

## Limitations

- **q is the real price.** Terse, right-to-left and unlike anything a team already knows, with a
  small and expensive labour pool. The SQL and Python layers postpone the need rather than remove
  it — until the first query that has to be fast.
- **No public price above 127 GiB, and none at all for a classic licence.** A small shop can
  budget the slider; anything else is a sales cycle.
- **The free edition is capped where tick data gets interesting.** 16GB is not a desk's intraday
  book, and one instance rules out a real tickerplant-plus-RDB-plus-HDB layout across machines.
  The licence also forbids building anything that competes with KX.
- **KX's benchmarks are KX's.** Its November 2025 TSBS run reports geometric-mean query ratios of
  3.36x against QuestDB and 161.3x against ClickHouse — vendor hardware, and a DevOps workload
  rather than a tick workload.
- **An individual backtester should not buy this.** One person with ten years of daily bars is
  better served by Parquet files and DuckDB, and will be finished before the q tutorial is.

## Alternatives

[QuestDB](https://stockmarketstack.com/tools/questdb) and [ClickHouse](https://stockmarketstack.com/tools/clickhouse) are the columnar engines people reach for first, both queried in SQL.
[TimescaleDB](https://stockmarketstack.com/tools/timescaledb) keeps you in Postgres; [ArcticDB](https://stockmarketstack.com/tools/arcticdb) stores versioned DataFrames on object storage with no
server; DuckDB over Parquet is the answer for a single researcher. What none replaces cleanly is
the tickerplant-to-HDB pattern and `aj` on a billion rows — which is why kdb+ is still on the desk
after twenty-five years.

## FAQ

### Is kdb+ the same thing as KDB-X?

KDB-X is the current distribution of the kdb+ engine, generally available since 17 November 2025 and now at 5.0, released 2026-07-23. KX describes it as retaining the same core engine with existing q code and data remaining compatible. The kdb+ 4.1 line is still shipped inside KX's kdb Insights product.

### Is there still a free kdb+ Personal Edition?

No. The old personal-edition download and its licence agreement now redirect to the KDB-X Community Edition and to the KX legal centre. The Community Edition replaces it, and unlike the personal edition it permits commercial use and runs offline.

### What does a commercial kdb+ licence cost?

KX publishes a RAM-based price list for KDB-X that starts at $1,822.92 a month for 32 GiB and reaches $11,437.50 at 127 GiB, with 128 GiB and above quoted by sales. The kdb+ product page itself carries no figure, and a classic k4.lic licence is still a conversation with sales@kx.com.

### Do I have to learn q to use it?

For anything serious, yes. There is a Python interface and a SQL module that translates a subset of ANSI SQL into q at runtime, but the tick architecture, the joins and every performance decision are written and tuned in q, and q is the part a team cannot hire for easily.

## Also from KX

- [OneTick](https://stockmarketstack.com/tools/onetick.md)

## Also worth comparing

- [ArcticDB](https://stockmarketstack.com/tools/arcticdb.md) — Versioned Pandas frames written straight onto S3, with no server to run.
- [DolphinDB](https://stockmarketstack.com/tools/dolphindb.md) — Closed-source tick database with a vector language, as-of joins and streaming engines.
- [InfluxDB 3](https://stockmarketstack.com/tools/influxdb.md) — Line-protocol time-series database rewritten on Arrow, DataFusion and Parquet.
- [QuestDB](https://stockmarketstack.com/tools/questdb.md) — Open-source time-series SQL built for tick data — ASOF JOIN, SAMPLE BY, LATEST ON.
- [Apache Druid](https://stockmarketstack.com/tools/druid.md) — Real-time OLAP cluster built for high-concurrency dashboards, not for research joins.
- [ClickHouse](https://stockmarketstack.com/tools/clickhouse.md) — Columnar OLAP database that keeps years of ticks on disk cheaply and scans them fast.