How Kubernetes is Built with Kat Cosgrove

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Kubernetes is the second-largest open-source project in the world. What does it actually do—and why is it so widely adopted?

In this episode of The Pragmatic Engineer, I’m joined by Kat Cosgrove, who has led several Kubernetes releases. Kat has been contributing to Kubernetes for several years, and originally got involved with the project through K3s (the lightweight Kubernetes distribution).

In our conversation, we discuss how Kubernetes is structured, how it scales, and how the project is managed to avoid contributor burnout.

We also go deep into: 

• An overview of what Kubernetes is used for

• A breakdown of Kubernetes architecture: components, pods, and kubelets

• Why Google built Borg, and how it evolved into Kubernetes

• The benefits of large-scale open source projects—for companies, contributors, and the broader ecosystem

• The size and complexity of Kubernetes—and how it’s managed

• How the project protects contributors with anti-burnout policies

• The size and structure of the release team

• What KEPs are and how they shape Kubernetes features

• Kat’s views on GenAI, and why Kubernetes blocks using AI, at least for documentation

• Where Kat would like to see AI tools improve developer workflows

• Getting started as a contributor to Kubernetes—and the career and networking benefits that come with it

• And much more!

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Timestamps

(00:00) Intro

(02:02) An overview of Kubernetes and who it’s for 

(04:27) A quick glimpse at the architecture: Kubernetes components, pods, and cubelets

(07:00) Containers vs. virtual machines 

(10:02) The origins of Kubernetes 

(12:30) Why Google built Borg, and why they made it an open source project

(15:51) The benefits of open source projects 

(17:25) The size of Kubernetes

(20:55) Cluster management solutions, including different Kubernetes services

(21:48) Why people contribute to Kubernetes 

(25:47) The anti-burnout policies Kubernetes has in place 

(29:07) Why Kubernetes is so popular

(33:34) Why documentation is a good place to get started contributing to an open-source project

(35:15) The structure of the Kubernetes release team 

(40:55) How responsibilities shift as engineers grow into senior positions

(44:37) Using a KEP to propose a new feature—and what’s next

(48:20) Feature flags in Kubernetes 

(52:04) Why Kat thinks most GenAI tools are scams—and why Kubernetes blocks their use

(55:04) The use cases Kat would like to have AI tools for

(58:20) When to use Kubernetes 

(1:01:25) Getting started with Kubernetes 

(1:04:24) How contributing to an open source project is a good way to build your network

(1:05:51) Rapid fire round

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The Pragmatic Engineer deepdives relevant for this episode:

•⁠ Backstage: an open source developer portal

•⁠ How Linux is built with Greg Kroah-Hartman

•⁠ Software engineers leading projects

•⁠ What TPMs do and what software engineers can learn from them

•⁠ Engineering career paths at Big Tech and scaleups

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See the transcript and other references from the episode at ⁠⁠https://newsletter.pragmaticengineer.com/podcast⁠⁠

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