Writing Post-Mortems: A Tech Lead's Guide to Learning from Failure
Turning Failures into Opportunities: How to Write Post-Mortems That Drive Real Change
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🚀 TL;DR
Incidents happen. Systems go down. Features break. Post-mortems are your chance to make sure it doesn’t happen the same way twice. Done right, they’re not just a retrospective, they’re a tool for continuous improvement, cultural alignment, and system resilience.
What Will We Dive Into Today? 📖
What are Post-Mortems For?
When should you write a post mortem?
What Post-Mortems are not for!
Why Post-Mortems matter
Pre-Mortems and when to write them
Deeper Post-Mortem Insights (Paid)
How to write a Post-Mortem (Sections & Examples)
Real World Examples (5 public post-mortems)
How to Define Action Items Your Team Will Actually Get Done
What Are Post-Mortems For? 🤔
Post-mortems are not documentation for the sake of formality. They are high-value tools designed to:
1️⃣ Understand What Really Happened
Dissect incidents to uncover what went wrong—not just on the surface, but at the root. Was it a code bug? A flawed assumption? A communication gap?
Focus on facts: timelines, metrics, and logs. Strip out opinions and bias.
2️⃣ Quantify the Impact
Who or what was affected? Downtime? Revenue loss? Customer trust?
Quantifying impact ensures the organization understands the stakes and aligns on the importance of solving the issue.
3️⃣ Identify Root Causes
The goal isn’t just to patch the issue but to address the underlying cause. Was it technical debt? Lack of monitoring? A systemic failure in decision-making?
Use frameworks like the Five Whys or Fishbone Diagrams to get to the root.
4️⃣ Drive Actionable Fixes
Clear, measurable action items are the cornerstone of a good post-mortem. Every recommendation should directly reduce risk or improve processes.
When you think of post-mortems, think of them as a chance to turn one failure into 10 future wins.
When Should You Write a Post-Mortem? 🛠️
Write post-mortems for:
Critical Failures: Major outages, severe performance degradations, or incidents impacting a significant number of users or revenue.
Recurrent Issues: When smaller problems happen repeatedly, signaling a deeper issue.
Unexpected Edge Cases: When the unexpected happens, and you realize your system isn’t as robust as you thought.
Even in non-catastrophic incidents, a lightweight post-mortem can provide insights that save you from bigger problems down the road.
What Post-Mortems Are NOT For 🚫
Let’s be clear about what post-mortems should avoid:
Blame Assignments
"Who broke it?" is the wrong question. Instead, ask, "What process or system allowed this to happen?" Create accountability, not blame.
Fluff and Buzzwords
A post-mortem isn’t a PR piece. Be direct, be honest, and use plain language. You’re solving problems, not telling stories.
Laundry Lists of Action Items
Too many tasks dilute focus. Prioritize the 2–3 fixes that will have the biggest impact.
A post-mortem should empower your team, not create confusion or resentment.
Why Post-Mortems Matter 🌟
A strong post-mortem culture makes your team resilient. Here’s how:
System Improvements: Identify weak points and strengthen your architecture.
Team Collaboration: Encourage open discussions without fear of judgment.
Organizational Growth: Create a culture where failure is seen as an opportunity to improve.
Great engineering teams embrace post-mortems as part of their DNA.
💡 Pre-Mortems: Fix Problems Before They Happen
You don’t have to wait for failure to improve. Enter pre-mortems: a proactive approach to anticipate and mitigate risks before launching something big.
What Is a Pre-Mortem?
Think of it as reverse-engineering failure. You imagine a scenario where your project crashes and burns, then work backward to figure out why it happened.
How to Run a Pre-Mortem
1️⃣ Contact the right people
Bring together stakeholders: engineers, product managers, operations, and anyone involved in the launch. This doesn’t have to be in a meeting it can be done offline through a document.
2️⃣ Define Success
What does a successful launch look like? Align on goals and priorities.
3️⃣ Imagine Failure
Assume the release was a disaster. Ask, “What went wrong?” Encourage wild ideas and edge cases.
4️⃣ Identify Risks
Categorize risks: technical, operational, procedural, or even cultural.
Use tools like risk matrices to evaluate the probability and impact of each issue.
5️⃣ Plan Mitigations
For each high-risk scenario, define clear steps to reduce the likelihood or severity of the problem.
6️⃣ Document It
Treat the pre-mortem like a post-mortem, with a written summary and actionable items.
When to Use Pre-Mortems
High-Stakes Projects: Major launches, new architectures, or high-visibility initiatives.
Tight Deadlines: When you know failure margins are slim.
Complex Dependencies: When multiple systems, teams, or vendors are involved.
Pre-mortems make you proactive, not reactive, and turn “what if” into “we’re ready.”
🚀 Too Long; Did Read
Post-Mortems: Learn from failures. Focus on facts, root causes, and actionable fixes.
Pre-Mortems: Anticipate failure before it happens. Use structured exercises to uncover risks and plan mitigations.
Both mechanisms create a culture where failure isn’t feared, it’s harnessed for growth.
What’s one insight you’ve gained from a post-mortem or pre-mortem? Let’s talk in the comments. 👇
💡 Exclusive for Paid Subscribers: Dive Deeper
In the paid section, we’ll explore:
1️⃣ How to structure your post-mortem for maximum impact using industry-proven frameworks.
2️⃣ 5 Real-world examples of post-mortems (With Reference Links) from the largest companies.
3️⃣ How to define actionable next steps that your team actually follows.
1️⃣ The Anatomy of a Great Post-Mortem
There isn’t one single correct way to write a post-mortem, it can take on whatever flavor best suits your team and organization. However, the most impactful and actionable post-mortems tend to follow a solid foundation like the template outlined below. A great post-mortem isn’t just a collection of facts, it’s a structured narrative that makes the problem and its solutions clear to everyone, from junior engineers to senior leadership.
Here’s what every section of a post-mortem should accomplish:
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