Camunda 8 Zeebe Broker Explained for Beginners

A Simple Guide to How Camunda 8 Really Works

Introduction

If you are new to Camunda 8, one term appears everywhere:

❓ Zeebe Broker

But what exactly is it?

Is it a database?
Is it a message broker?
Is it the workflow engine?

👉 The short answer:
Zeebe Broker is the heart of Camunda 8.

In this blog, we explain:

• What Zeebe Broker is

• Why it exists

• How it works internally

• How it executes BPMN

• How it scales

• What beginners must know to use it safely

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What Is the Zeebe Broker?

The Zeebe Broker is the distributed workflow engine behind Camunda 8.

It is responsible for:

• Executing BPMN workflows

• Persisting workflow state

• Handling messages & jobs

• Distributing work across nodes

• Guaranteeing fault tolerance

Unlike Camunda 7, Zeebe is:

• Event-driven

• Log-based

• Clustered by design

👉 Think of Zeebe as a workflow state machine built on a distributed log.

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Zeebe Is NOT a Traditional Database or Queue

Many beginners misunderstand Zeebe.

❌ What Zeebe is NOT

• ❌ Not a relational database

• ❌ Not Kafka

• ❌ Not RabbitMQ

• ❌ Not just a job queue

✅ What Zeebe actually is

• A distributed workflow engine

• An append-only log system

• A stream processor

• A state machine for BPMN

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High-Level Architecture

Core components

BPMN Workflow
      ↓
Zeebe Broker
      ↓
Distributed Log
      ↓
Stream Processor
      ↓
State (in-memory + RocksDB)

Other Camunda 8 services:

• Operate – Monitoring & debugging

• Tasklist – Human tasks

• Optimize – Analytics

• Identity – Auth

• External Workers – Business logic

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How Zeebe Executes a BPMN Workflow

Let’s say you deploy and start a process.

Step-by-step

1. BPMN is deployed to Zeebe

2. You start a workflow instance

3. Zeebe writes an event to the log

4. Stream processors consume the event

5. State is updated

6. Next BPMN step is activated

7. Jobs are created for workers

8. Workers complete jobs

9. New events are written

Event → Log → Processing → State → Next Step → Event

👉 Everything in Zeebe is event-driven.

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Why Zeebe Uses an Append-Only Log

This is the most important concept.

Traditional engines (Camunda 7)

BPMN → DB transaction → Commit → Next step

Zeebe (Camunda 8)

BPMN → Event → Append to Log → Process → Update State

Benefits

✔ Horizontal scalability
✔ Fault tolerance
✔ Replayable state
✔ High throughput

Trade-off

❌ No traditional rollback
❌ Eventual consistency
❌ Requires compensation logic

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What Is a Zeebe Partition?

A partition is a slice of workflow data.

• Each partition has:

  • A leader

  • One or more followers

• Leaders handle:

  • Writes

  • Job creation

• Followers replicate data

Partition 1 → Broker A (Leader)
Partition 2 → Broker B (Leader)
Partition 3 → Broker C (Leader)

👉 Partitions are how Zeebe scales horizontally.

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What Happens If a Broker Node Fails?

Zeebe is fault-tolerant.

Failure scenario

1. Broker A crashes

2. Partition leader disappears

3. A follower is elected leader

4. Processing continues

👉 No data loss.
👉 No manual restart required.

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How Jobs & Workers Work in Zeebe

Zeebe does not execute your business logic.

Instead:

1. BPMN reaches a Service Task

2. Zeebe creates a job

3. External workers poll for jobs

4. Worker executes logic

5. Worker completes job

6. Zeebe continues workflow

BPMN → Job → Worker → Complete → Next Step

👉 All logic is external.

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Why Zeebe Feels “Different” from Camunda 7

Concept	Camunda 7	Camunda 8 (Zeebe)
Execution	DB transactions	Event-driven
State	Relational DB	Log + State store
Rollback	Yes	No (compensate)
Java delegates	Yes	No
External tasks	Optional	Mandatory
Scaling	Vertical	Horizontal
Consistency	Strong	Eventual

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Beginner Mistakes 🚨

❌ Expecting synchronous execution
❌ Expecting rollback
❌ Embedding Java logic
❌ Modifying variables like a DB row
❌ Treating Zeebe like Kafka
❌ Ignoring worker failures

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When Zeebe Is the Right Choice

✔ Cloud-native systems
✔ Microservices
✔ High throughput
✔ Event-driven architectures
✔ Distributed orchestration
✔ New greenfield projects

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When Zeebe Is NOT the Right Choice

❌ Heavy transactional workflows
❌ Strong ACID requirements
❌ Human-task-heavy systems
❌ On-premise monoliths
❌ Teams new to async systems

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Interview Question (Very Common)

Q: What is the Zeebe Broker in Camunda 8?
A: A distributed, log-based workflow engine that executes BPMN using event sourcing.

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Final Takeaway

❗ Zeebe is not “Camunda 7 but faster”.
❗ It is a completely different execution model.

If you understand:

• Event sourcing

• Append-only logs

• External workers

• Eventual consistency

Then Zeebe is incredibly powerful.

If not, Camunda 7 is often the safer choice.

💼 Professional Support Available

If you are facing issues in real projects related to enterprise backend development or workflow automation, I provide paid consulting, production debugging, project support, and focused trainings.

Technologies covered include Java, Spring Boot, PL/SQL, Azure, and workflow automation (jBPM, Camunda BPM, RHPAM).

📧 Contact: ishikhanirankari@gmail.com | info@realtechnologiesindia.com

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