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What is pulsar?

apache/pulsar — explained in plain English

Analysis updated 2026-06-24

★ 15,236JavaAudience · ops devopsComplexity · 5/5LicenseSetup · hard

In one sentence

Apache Pulsar is a distributed messaging system, like a postal service for software, that moves millions of messages per second across services with geo-replication and multi-tenant isolation built in.

Mindmap

mindmap
  root((apache-pulsar))
    What it does
      Pub-sub messaging
      Millions of topics
      Real-time streaming
    Key Features
      Geo-replication
      Multi-tenancy
      Queue and stream
    Client Libraries
      Java Go Python
      Node.js .NET C++
    Operations
      REST admin API
      Load balancing
      Auth and quotas
    Audience
      Platform engineers
      Distributed systems
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What do people build with it?

USE CASE 1

Build an event-driven microservices backbone that decouples producers and consumers at millions of messages per second.

USE CASE 2

Replace a messaging cluster with Pulsar to get built-in geo-replication between data centers without extra tooling.

USE CASE 3

Set up a multi-tenant messaging platform where different teams get isolated topics with their own authentication and quotas on one shared cluster.

USE CASE 4

Stream data between regions using Pulsar geo-replication for disaster recovery or globally distributed writes.

What is it built with?

JavaGradleGoPythonC++Node.js.NET

How does it compare?

apache/pulsarapache/doriszaproxy/zaproxy
Stars15,23615,33315,120
LanguageJavaJavaJava
Setup difficultyhardhardmoderate
Complexity5/54/54/5
Audienceops devopsdatadeveloper

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · hard Time to first run · 1h+

Requires running a Pulsar broker on JDK 21 plus ZooKeeper and BookKeeper, Docker Compose is the fastest path for local testing.

Use freely for any purpose, including commercial use, as long as you include the Apache 2.0 license notice.

So what is it?

Apache Pulsar is a distributed pub-sub messaging system, a kind of postal service for software, where one part of an application publishes messages on a named channel (called a topic) and other parts subscribe to receive them. It is built to move very large amounts of data between services, supporting millions of independent topics and millions of messages per second. It offers strong ordering and consistency guarantees, meaning messages arrive reliably and in the order they were sent, and it supports both topic streaming (a continuous feed of events) and queue semantics (work items picked up one at a time). Pulsar is designed to run as a hosted service: it includes multi-tenancy (multiple teams sharing one cluster with their own authentication, authorization, and quotas), a load balancer, geo-replication (copying data between data centers), and transparent handling of partitioned topics and message batching. It also tracks each consumer's position in the message stream and exposes a REST API for provisioning, administration, and stats. Teams typically reach for Pulsar when they need a backbone for event streaming, message queuing, or decoupling services at scale, especially across multiple regions or tenants. The core is written in Java and built with Gradle. Recent versions (4.x and master) target JDK 21 for the broker, with the command-line tools and Java client supporting JDK 17 or 21. Official client libraries are maintained for .NET/C#, C++, Go, Node.js, Python, and a reactive Java variant. The project is part of the Apache Software Foundation and licensed under Apache 2.0. The full README is longer than what was provided.

Copy-paste prompts

Prompt 1
Set up a local Apache Pulsar cluster and write a Java producer that publishes 1000 messages per second to a topic called orders, then a consumer that prints each message.
Prompt 2
How do I configure Pulsar geo-replication to sync messages between two clusters in different regions? Show me the admin CLI commands.
Prompt 3
I am migrating from Kafka to Pulsar. What are the key differences in how topics, consumer groups, and offset management work?
Prompt 4
Write a Python Pulsar consumer that reads from a partitioned topic, acknowledges messages individually, and handles connection failures with retries.
Prompt 5
How does Pulsar multi-tenancy work? Show me the admin commands to create a tenant, a namespace, and a topic with its own auth policy.

Frequently asked questions

What is pulsar?

Apache Pulsar is a distributed messaging system, like a postal service for software, that moves millions of messages per second across services with geo-replication and multi-tenant isolation built in.

What language is pulsar written in?

Mainly Java. The stack also includes Java, Gradle, Go.

What license does pulsar use?

Use freely for any purpose, including commercial use, as long as you include the Apache 2.0 license notice.

How hard is pulsar to set up?

Setup difficulty is rated hard, with roughly 1h+ to a first successful run.

Who is pulsar for?

Mainly ops devops.

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