Spotlight on SIG Apps

By Sandipan Panda (DevZero) | Wednesday, March 12, 2025

In our ongoing SIG Spotlight series, we dive into the heart of the Kubernetes project by talking to the leaders of its various Special Interest Groups (SIGs). This time, we focus on SIG Apps, the group responsible for everything related to developing, deploying, and operating applications on Kubernetes. Sandipan Panda (DevZero) had the opportunity to interview Maciej Szulik (Defense Unicorns) and Janet Kuo (Google), the chairs and tech leads of SIG Apps. They shared their experiences, challenges, and visions for the future of application management within the Kubernetes ecosystem.

Introductions

Sandipan: Hello, could you start by telling us a bit about yourself, your role, and your journey within the Kubernetes community that led to your current roles in SIG Apps?

Maciej: Hey, my name is Maciej, and I’m one of the leads for SIG Apps. Aside from this role, you can also find me helping SIG CLI and also being one of the Steering Committee members. I’ve been contributing to Kubernetes since late 2014 in various areas, including controllers, apiserver, and kubectl.

Janet: Certainly! I'm Janet, a Staff Software Engineer at Google, and I've been deeply involved with the Kubernetes project since its early days, even before the 1.0 launch in 2015. It's been an amazing journey!

My current role within the Kubernetes community is one of the chairs and tech leads of SIG Apps. My journey with SIG Apps started organically. I started with building the Deployment API and adding rolling update functionalities. I naturally gravitated towards SIG Apps and became increasingly involved. Over time, I took on more responsibilities, culminating in my current leadership roles.

About SIG Apps

All following answers were jointly provided by Maciej and Janet.

Sandipan: For those unfamiliar, could you provide an overview of SIG Apps' mission and objectives? What key problems does it aim to solve within the Kubernetes ecosystem?

As described in our charter, we cover a broad area related to developing, deploying, and operating applications on Kubernetes. That, in short, means we’re open to each and everyone showing up at our bi-weekly meetings and discussing the ups and downs of writing and deploying various applications on Kubernetes.

Sandipan: What are some of the most significant projects or initiatives currently being undertaken by SIG Apps?

At this point in time, the main factors driving the development of our controllers are the challenges coming from running various AI-related workloads. It’s worth giving credit here to two working groups we’ve sponsored over the past years:

The Batch Working Group, which is looking at running HPC, AI/ML, and data analytics jobs on top of Kubernetes.
The Serving Working Group, which is focusing on hardware-accelerated AI/ML inference.

Best practices and challenges

Sandipan: SIG Apps plays a crucial role in developing application management best practices for Kubernetes. Can you share some of these best practices and how they help improve application lifecycle management?

Implementing health checks and readiness probes ensures that your applications are healthy and ready to serve traffic, leading to improved reliability and uptime. The above, combined with comprehensive logging, monitoring, and tracing solutions, will provide insights into your application's behavior, enabling you to identify and resolve issues quickly.
Auto-scale your application based on resource utilization or custom metrics, optimizing resource usage and ensuring your application can handle varying loads.
Use Deployment for stateless applications, StatefulSet for stateful applications, Job and CronJob for batch workloads, and DaemonSet for running a daemon on each node. Use Operators and CRDs to extend the Kubernetes API to automate the deployment, management, and lifecycle of complex applications, making them easier to operate and reducing manual intervention.

Sandipan: What are some of the common challenges SIG Apps faces, and how do you address them?

The biggest challenge we’re facing all the time is the need to reject a lot of features, ideas, and improvements. This requires a lot of discipline and patience to be able to explain the reasons behind those decisions.

Sandipan: How has the evolution of Kubernetes influenced the work of SIG Apps? Are there any recent changes or upcoming features in Kubernetes that you find particularly relevant or beneficial for SIG Apps?

The main benefit for both us and the whole community around SIG Apps is the ability to extend kubernetes with Custom Resource Definitions and the fact that users can build their own custom controllers leveraging the built-in ones to achieve whatever sophisticated use cases they might have and we, as the core maintainers, haven’t considered or weren’t able to efficiently resolve inside Kubernetes.

Contributing to SIG Apps

Sandipan: What opportunities are available for new contributors who want to get involved with SIG Apps, and what advice would you give them?

We get the question, "What good first issue might you recommend we start with?" a lot :-) But unfortunately, there’s no easy answer to it. We always tell everyone that the best option to start contributing to core controllers is to find one you are willing to spend some time with. Read through the code, then try running unit tests and integration tests focusing on that controller. Once you grasp the general idea, try breaking it and the tests again to verify your breakage. Once you start feeling confident you understand that particular controller, you may want to search through open issues affecting that controller and either provide suggestions, explaining the problem users have, or maybe attempt your first fix.

Like we said, there are no shortcuts on that road; you need to spend the time with the codebase to understand all the edge cases we’ve slowly built up to get to the point where we are. Once you’re successful with one controller, you’ll need to repeat that same process with others all over again.

Sandipan: How does SIG Apps gather feedback from the community, and how is this feedback integrated into your work?

We always encourage everyone to show up and present their problems and solutions during our bi-weekly meetings. As long as you’re solving an interesting problem on top of Kubernetes and you can provide valuable feedback about any of the core controllers, we’re always happy to hear from everyone.

Looking ahead

Sandipan: Looking ahead, what are the key focus areas or upcoming trends in application management within Kubernetes that SIG Apps is excited about? How is the SIG adapting to these trends?

Definitely the current AI hype is the major driving factor; as mentioned above, we have two working groups, each covering a different aspect of it.

Sandipan: What are some of your favorite things about this SIG?

Without a doubt, the people that participate in our meetings and on Slack, who tirelessly help triage issues, pull requests and invest a lot of their time (very frequently their private time) into making kubernetes great!

SIG Apps is an essential part of the Kubernetes community, helping to shape how applications are deployed and managed at scale. From its work on improving Kubernetes' workload APIs to driving innovation in AI/ML application management, SIG Apps is continually adapting to meet the needs of modern application developers and operators. Whether you’re a new contributor or an experienced developer, there’s always an opportunity to get involved and make an impact.

If you’re interested in learning more or contributing to SIG Apps, be sure to check out their SIG README and join their bi-weekly meetings.