This article is based on an interview originally published by ITPro Today with CircleCI CTO Rob Zuber, conducted around the time of the company’s Series D funding announcement in July 2019.
Background: CircleCI and Its Series D Round
CircleCI is one of the most recognized names in the continuous integration and continuous deployment (CI/CD) space. In July 2019, the company announced it had raised $56 million in a Series D funding round, underscoring investor confidence in the DevOps tooling market at the time.
At the center of CircleCI’s technical direction is CTO Rob Zuber, who joined the company in 2014. Zuber had previously co-founded Copious alongside Jim Rose, who went on to become CircleCI’s CEO. In an interview with ITPro Today, Zuber outlined the company’s mission, the changing shape of the CI/CD market, and what comes next.
What Is CircleCI’s Core Mission?
According to Zuber, CircleCI’s purpose is straightforward: help software developers and engineering organizations deliver value to their customers faster and more reliably.
“We’re all about helping those teams execute quickly and get the value that’s in their heads into the hands of their customers.”
Rob Zuber, CTO, CircleCI
Zuber frames this in the context of a world where virtually every organization — from banks to retailers — differentiates on the quality and speed of its software. Customers now choose services based on the quality of the digital experience, making internal engineering capability a direct competitive advantage.
Practically speaking, CircleCI sits in the pipeline between a developer committing code and that code reaching production. That includes validating code, building packages, producing artifacts, and orchestrating deployment into production environments.
Why Was CircleCI Still Raising Capital?
Zuber’s explanation for the Series D is rooted in market dynamics rather than internal need. The CI/CD and DevOps tooling market was expanding, and CircleCI had consolidated a strong position as many of its earlier competitors exited the space.
“We had a cohort of competitors, most of whom have disappeared over the last couple of years.”
Rob Zuber, CTO, CircleCI
With demonstrated unit economics — customers paying for measurable value — CircleCI was able to show investors a sustainable growth trajectory. Additional capital meant the ability to accelerate that growth by investing in the platform, expanding integrations, and deepening enterprise relationships.
How Has the CI/CD Market Evolved Since 2012?
Zuber traces CircleCI’s market history through several distinct technology waves, each of which reshaped what CI/CD tooling needed to do.
The Ruby on Rails Era
CircleCI’s earliest growth came from developers building Ruby on Rails applications. The Rails ecosystem had a strong cultural emphasis on automated testing from the start, which aligned naturally with CI/CD principles. Developers excited about Rails were, almost by default, excited about testing — making them ideal early adopters.
Docker and Containerization
The release of Docker in 2013 marked a significant turning point. Containerization changed how software was built and shipped, driving adoption of microservices architectures. CI/CD platforms had to evolve to support building within Docker containers, producing Docker images, and pushing those images to container registries.
Kubernetes Wins Container Orchestration
The container orchestration landscape initially fragmented across many competing platforms — what Zuber describes as “a thousand flowers bloom.” That period eventually resolved decisively in Kubernetes’ favor, with most other orchestration systems either folding or repositioning as wrappers around Kubernetes. CI/CD tooling, including CircleCI, adapted accordingly.
How Did CircleCI’s Platform Approach Change?
Zuber describes a deliberate architectural shift between CircleCI’s 1.0 and 2.0 platforms. The 1.0 approach was opinionated — CircleCI made assumptions about how software should be built. The 2.0 platform moved toward flexibility, giving teams the tools to define their own build processes as the broader ecosystem continued to evolve.
A key capability introduced in the 2.0 era is Orbs — reusable, shareable packages of CI/CD configuration. Orbs allow the community to encode and distribute best practices for integrating with specific tools, frameworks, or cloud providers, effectively crowdsourcing platform extensibility.
- Orbs are shareable configuration packages that encapsulate CI/CD steps for common workflows.
- They reduce duplication across projects and allow teams to adopt community-maintained integrations.
- The model acknowledges that the tooling ecosystem evolves faster than any single vendor can track internally.
How Have Programming Languages Shifted in the CI/CD Context?
Zuber notes that the mix of programming languages seen across CI/CD pipelines shifts over time, often driven by corporate sponsorship and platform alignment rather than purely technical merit.
- Kotlin saw rapid adoption after Google endorsed it as the preferred language for Android development, driving a large wave of Android-focused CI/CD pipelines.
- Swift grew significantly in the iOS ecosystem following Apple’s promotion of the language as a replacement for Objective-C.
These examples illustrate how platform decisions by major technology companies can rapidly reshape the workloads that CI/CD systems need to support.
What Was Next for CircleCI at the Time?
Looking ahead from mid-2019, Zuber identified two primary focus areas:
- Core CI/CD experience: Continuing to reduce friction in onboarding and ensuring that the platform scales as engineering organizations grow. The goal was to keep the entry point simple while providing depth for sophisticated teams.
- Data-driven development insights: Moving beyond individual pipeline runs toward aggregate analytics — surfacing patterns in how teams deliver software, identifying bottlenecks, and helping engineering organizations make better structural decisions based on data from their own pipelines.
“Taking all of that knowledge we have on development and giving it back — giving users better insight into their projects… how they can be better in terms of how they deliver software through data insights.”
Rob Zuber, CTO, CircleCI
Key Takeaways for DevOps Practitioners
Zuber’s perspective in this 2019 interview reflects broader trends that have continued to define the DevOps tooling market:
- CI/CD is no longer a niche developer tool — it is infrastructure-level software delivery capability for any organization that ships software.
- Platform flexibility (rather than opinionated defaults) is increasingly important as the underlying technology stack — containers, orchestration, languages — continues to shift.
- Community-driven extensibility models, like CircleCI’s Orbs, reflect a realistic acknowledgment that no single vendor can keep pace with the full ecosystem.
- The next frontier for CI/CD tooling is not just automation but insight — using pipeline data to improve engineering processes at an organizational level.
Original interview by Sean Michael Kerner, published on ITPro Today.