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Immutable Ordered Key-Value Database Engine
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Problem: PumpkinDB is not *really* an event sourcing database engine
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Build status (Linux) Build Status
Build status (Windows) Windows Build status
Project status Usable, between alpha and beta
Production-readiness Depends on your risk tolerance

PumpkinDB is an immutable ordered key-value database engine, featuring:

  • ACID transactions
  • Persistent storage
  • An embedded programming language (PumpkinScript)
  • Binary keys and values (allows any encoding to be used: JSON, XML, Protobuf, Cap'n Proto, etc.)
  • Standalone and embedded scenarios

Why immutable?

Simply put, the data replaced is data deleted and is therefore, an unsafe way to manage data. Bugs, misunderstanding, changing scope and requirements and other factors might influence what data (and especially past data) means and how can it be used.

By guaranteeing the immutability of key's value once it is set, PumpkinDB forces its users to think of their data through a temporal perspective.

This approach is highly beneficial for implementing event sourcing and similar types of architectures.

What is PumpkinDB?

PumpkinDB is essentially a database programming environment, largely inspired by core ideas behind MUMPS. Instead of M, it has a Forth-inspired stack-based language, PumpkinScript. Instead of hierarchical keys, it has a flat key namespace and doesn't allow overriding values once they are set. Core motivation for immutability was that with the cost of storage declining, erasing data is effectively a strategical mistake.

While not intended for general purpose programming, its main objective is to facilitate building specialized application-specific and generic databases with a particular focus on immutability and processing data as close to storage as possible, incurring as little communication penalty as possible.

Applications communicate with PumpkinDB by sending small PumpkinScript programs over a network interface (or API when using PumpkinDB as an embedded solution).

PumpkinDB offers a wide array of primitives for concurrency, storage, journalling, indexing and other common building blocks.

Why is it a database engine?

The core ideas behind PumpkinDB stem from the so called lazy event sourcing approach which is based on storing and indexing events while delaying domain binding for as long as possible. That said, the intention of this database is to be a building block for different kinds of architectures, be it classic event sourcing (using it as an event store), lazy event sourcing (using indices) or anything else. It's also possible to implement different approaches within a single database for different parts of the domain.

Instead of devising custom protocols for talking to PumpkinDB, the protocol of communication has become a pipeline to a script executor. This offers us enormous extension and flexibility capabilities.

While an external application can talk to PumpkinDB over a network connection, PumpkinDB's engine itself is embeddable and can be used directly. Currenly, it is available for Rust applications only, but this may one day extend to all languages that can interface with C.

Client libraries

Language Library Status
Rust pumpkindb_client Early release (0.2.0)
Java pumpkindb-client Pre-release

Trying it out

You can download PumpkinDB releases from GitHub.


You can try out latest PumpkinDB HEAD revision by using a docker image:

$ docker pull pumpkindb/pumpkindb

Alternatively, you can build the image yourself:

$ docker build . -t pumpkindb/pumpkindb

Run the server:

$ docker run -p 9981:9981 -ti pumpkindb/pumpkindb
2017-04-12T02:52:47.440873517+00:00 WARN pumpkindb - No logging configuration specified, switching to console logging
2017-04-12T02:52:47.440983318+00:00 INFO pumpkindb - Starting up
2017-04-12T02:52:47.441122740+00:00 INFO pumpkindb_engine::storage - Available disk space is approx. 56Gb, setting database map size to it
2017-04-12T02:52:47.441460231+00:00 INFO pumpkindb - Starting 4 schedulers
2017-04-12T02:52:47.442375937+00:00 INFO pumpkindb - Listening on

Finally, connect to it using pumpkindb-term:

$ docker run -ti pumpkindb/pumpkindb pumpkindb-term # replace IP with the docker host IP

Building from the source code

You are also welcome to clone the repository and build it yourself. You will need Rust Nightly to do this. The easiest way to get it is to use rustup

$ rustup install nightly
$ rustup override set nightly # in PumpkinDB directory

After that, you can run PumpkinDB server this way:

$ cargo build --all
$ ./target/debug/pumpkindb
2017-04-03T10:43:49.667667-07:00 WARN pumpkindb - No logging configuration specified, switching to console logging
2017-04-03T10:43:49.668660-07:00 INFO pumpkindb - Starting up
2017-04-03T10:43:49.674139-07:00 INFO pumpkindb_engine::storage - Available disk space is approx. 7Gb, setting database map size to it
2017-04-03T10:43:49.675759-07:00 INFO pumpkindb - Starting 8 schedulers
2017-04-03T10:43:49.676113-07:00 INFO pumpkindb - Listening on

You can connect to it using pumpkindb-term:

$ ./target/debug/pumpkindb-term
Connected to PumpkinDB at
To send an expression, end it with `.`
Type \h for help.


"John Doe"
"Jopn Doe"

(The above example shows how one can query and navigate for values submitted at a different time, using low level primitives).

You can change some of the server's parameters by creating pumpkindb.toml:

path = "path/to/db"
# By default, mapsize will equal to the size of
# available space on the disk, except on Windows,
# where default would be 1Gb.
# `mapsize` is a theoretical limit the database can
# grow to. However, on Windows, this also means that
# the database file will take that space.
# This parameter allows to specify the mapsize
# in megabytes.
# mapsize = 2048

port = 9981


PumpkinDB project is split into a couple of separate components (crates):

  • pumpkinscript — PumpkinScript parser. Allows to convert text PumpkinScript form into binary one.
  • pumpkindb_engine — Core PumpkinDB library. Provides PumpkinScript scheduler, and a standard library of instructions
  • pumpkindb_mio_server — Async MIO-based PumpkinDB server library. Useful for building custom PumpkinProtocol-compatible servers.
  • pumpkindb_client — PumpkinProtocol client library.
  • pumpkindb_server — Stock PumpkinDB server. Built on top of pumpkindb_mio_server.
  • pumpkindb_term — console-based PumpkinDB server client.
  • doctests — a small utility to run instructions doctests.


This project is in its very early days and we will always be welcoming contributors.

Our goal is to encourage frictionless contributions to the project. In order to achieve that, we use Unprotocols C4 process. Please read it, it will answer a lot of questions. Our goal is to merge pull requests as quickly as possible and make new stable releases regularly.

In a nutshell, this means:

  • We merge pull requests rapidly (try!)
  • We are open to diverse ideas
  • We prefer code now over consensus later

To learn more, read our contribution guidelines

We also maintain a list of issues that we think are good starters for new contributors.


Support us with a monthly donation and help us continue our activities. [Become a backer]


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