---
title: "Why is Kafka Fast?"
description: "Explore the key design choices behind Kafka's high performance."
image: "https://assets.bytebytego.com/diagrams/0424-why-is-kafka-fast.jpg"
createdAt: "2024-02-05"
draft: false
categories:
  - database-and-storage
tags:
  - "Kafka"
  - "Performance"
---

![No alternative text description for this image](https://assets.bytebytego.com/diagrams/0424-why-is-kafka-fast.jpg)

There are many design decisions that contributed to Kafka’s performance. In this post, we’ll focus on two. We think these two carried the most weight.

## Sequential I/O

The first one is Kafka’s reliance on Sequential I/O.

## Zero Copy

The second design choice that gives Kafka its performance advantage is its focus on efficiency: zero copy principle.

The diagram above illustrates how the data is transmitted between producer and consumer, and what zero-copy means.

*   Step 1.1 - 1.3: Producer writes data to the disk
*   Step 2: Consumer reads data without zero-copy
    *   2.1: The data is loaded from disk to OS cache
    *   2.2 The data is copied from OS cache to Kafka application
    *   2.3 Kafka application copies the data into the socket buffer
    *   2.4 The data is copied from socket buffer to network card
    *   2.5 The network card sends data out to the consumer
*   Step 3: Consumer reads data with zero-copy
    *   3.1: The data is loaded from disk to OS cache
    *   3.2 OS cache directly copies the data to the network card via sendfile() command
    *   3.3 The network card sends data out to the consumer

Zero copy is a shortcut to save multiple data copies between the application context and kernel context.