I introduced a critical bug in production
I Introduced a Critical Bug in Production: Lessons Learned
As a Senior Software Engineer (SSE) in frontend development with over three years of experience, I recently faced a challenging situation that many in the tech industry can relate to: I introduced a critical bug into production. This experience has been a humbling reminder of the importance of robust processes, testing, and team dynamics. In this post, I will share my experience, the lessons learned, and how to approach such situations in the future.
The Incident
It all started with a production deployment I made late one evening. The pull request (PR) I was merging was primarily intended to add instrumentation and improve error logging. However, it also contained a change to an API service function that modified its return type from an array to an object. While I updated the majority of the files consuming this function, I unfortunately missed one crucial file.
Since this change was deemed “just instrumentation” and did not involve any user interface (UI) alterations, the deployment bypassed our usual quality assurance (QA) checks. Five hours after the deployment, support reported that several paid features were inaccessible due to this oversight. Fortunately, the on-call engineer was able to resolve the issue quickly, but not without prompting discussions about root cause analysis (RCA) and the need for process improvements.
The Fallout
When reflecting on this incident, I was acutely aware of how it might affect my standing with my Engineering Manager (EM) and the team. This was my second RCA, and I worried that my reputation as a SSE was at stake. Although the on-call engineer was able to fix the issue swiftly, I felt the weight of responsibility for my oversight and the potential implications for the team.
Community Reactions
As I shared my experience with peers, their responses offered a mix of empathy, advice, and critiques. Some highlighted that the lack of QA was a systemic failure, while others pointed out that my decision to deploy late at night on a holiday was questionable. Many voiced that the absence of unit tests and integration tests in our codebase contributed to the problem, and that the team’s process needed significant improvement.
Here are some key takeaways from the community’s feedback:
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QA is Essential: The consensus was clear: all changes, regardless of their perceived impact, should undergo thorough QA. Skipping QA, even for what seems like minor changes, can lead to significant issues.
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Ownership and Accountability: Taking ownership of mistakes is crucial. Acknowledging the error and focusing on how to prevent it in the future demonstrates maturity and professionalism.
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Process Improvement: Rather than just reflecting on the mistake, I was encouraged to propose actionable changes to improve our deployment process, such as better integration tests, smoke tests, and a more robust CI/CD pipeline.
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Team Approach: Many emphasized that incidents like this are often team failures rather than individual ones. It’s essential to foster a blameless culture that encourages learning from mistakes without fear of retribution.
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Post-Mortem Culture: Conducting a blameless post-mortem allows teams to identify gaps in processes and systems, ultimately leading to improvements in quality and team morale.
Moving Forward
In light of the incident, I’ve taken several steps to ensure that similar mistakes do not recur:
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Advocating for Tests: I’ve committed to writing unit tests for the API functions I work on. This will help catch issues early and ensure that our code remains reliable.
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Enhancing Communication: I plan to communicate with my team more effectively about code changes and their implications, especially when they involve API modifications.
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Championing QA: I will advocate for establishing a QA process that includes all changes, regardless of their nature. Ensuring that thorough testing is part of our deployment checklist is essential.
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Reflecting on Processes: I’ll engage my team in discussions about our current processes and how we can improve them, including the necessity for a staging environment and better integration testing.
Conclusion
While introducing a critical bug in production is a daunting experience, it can also serve as a powerful learning opportunity. By taking ownership of the mistake, engaging in constructive discussions with my team, and advocating for improved processes, I can turn this incident into a catalyst for positive change.
Mistakes will happen, especially in a fast-paced environment like software development. However, how we respond and adapt to these challenges ultimately defines our growth as engineers and as a team. Let’s embrace the lessons learned from our missteps and strive for a culture of continuous improvement and accountability.