{"id":11803,"date":"2026-11-10T17:30:00","date_gmt":"2026-11-10T17:30:00","guid":{"rendered":"https:\/\/www.cotocus.com\/blog\/?p=11803"},"modified":"2026-11-10T17:30:00","modified_gmt":"2026-11-10T17:30:00","slug":"eight-release-failure-reasons","status":"publish","type":"post","link":"https:\/\/www.cotocus.com\/blog\/eight-release-failure-reasons\/","title":{"rendered":"8 Reasons Your Release Could Fail, Found Before It Ships"},"content":{"rendered":"

Picture the scene: your team’s major release went out on Thursday, and by Friday morning it has been rolled back. The retrospective is scheduled, and everyone is already composing explanations. Now rewind. If you could hold that retrospective today, before the release, what would it say? That question is the core of a pre-mortem, and for engineering teams it produces some remarkably consistent answers. Below are eight imagined causes of a failed release that appear again and again, with a note on how to test each one while the fix is still inexpensive.<\/p>\n

1. The environments never matched<\/h2>\n

The change worked in testing and failed in production because the two differed in some quiet way: a configuration value, a library version, a data volume. In the imagined post-mortem, someone says “but it passed in staging.” The preventive question is how closely staging mirrors production, and who is responsible for keeping it that way. If the answer is “nobody in particular,” that is your first finding.<\/p>\n

2. The deployment steps lived in one person’s head<\/h2>\n

Manual release procedures depend on memory. When the one engineer who knows the sequence is unavailable, or merely tired, steps get skipped. Imagine the failure and ask which step was forgotten. Writing the sequence down, or better, automating it, turns a personal skill into a team capability.<\/p>\n

3. The rollback was never rehearsed<\/h2>\n

Many teams have a rollback plan and never test it. In the imagined failure, the team discovers during the incident that the database change cannot be reversed or the previous version no longer builds. The preventive step is a rehearsal in a safe environment before the real event, with timing recorded.<\/p>\n

4. The delivery pipeline was trusted without being examined<\/h2>\n

Code reaches production through a chain of build, test and deploy steps. Each step holds credentials and authority, and each is a place where a mistake or misuse can slip through. For a readable overview of how engineers think about hardening that chain, the blog at DevSecOps Now<\/a> is a reasonable starting point, since it concentrates on securing CI\/CD pipelines. For the pre-mortem, the useful question is simple: which pipeline step, if altered or broken, would we notice last?<\/p>\n

5. A dependency changed underneath us<\/h2>\n

Modern software leans on many external components and services. In the imagined failure, an upstream change, an expired certificate or an unavailable service stops the release. The preventive habit is to list the dependencies that matter, record who monitors each, and agree what happens when one disappears.<\/p>\n

6. The model or data behaved differently in the real world<\/h2>\n

For teams shipping machine-learning features, a release can fail even when the code is perfect, because the live data no longer resembles the data used in training. This is a classic gap, and an overview of how operational practice for machine learning products fits together<\/a> gives useful vocabulary for it. In the pre-mortem, write the note “the model degraded quietly after launch” and then decide how you would detect that within days instead of months.<\/p>\n

7. Nobody was watching when it mattered<\/h2>\n

A release can go wrong at an inconvenient hour, and if alerts reach nobody, the problem grows. The imagined failure here is not the defect itself but the silence around it. Check that someone is clearly on call, that they know the release is happening, and that the signals they would see are meaningful. A look at how disciplined processes speed up model deployments<\/a> shows why monitoring is built into good delivery rather than added afterwards.<\/p>\n

8. The people side was ignored<\/h2>\n

Finally, a surprising number of failed releases trace back to communication. Support was not told what changed, customers were not warned of downtime, or a dependent team learned about the schedule from the release notes. Add a plain item to the pre-mortem: “who needed to know, and when did they find out?”<\/p>\n

How to use the list<\/h2>\n

These eight items are prompts, not a complete inventory. Your own pre-mortem will produce causes specific to your product, and those are the valuable ones. A workable format for the session looks like this:<\/p>\n

    \n
  1. State the premise: “The release has failed and we are in the review.”<\/li>\n
  2. Give each participant five minutes to write causes individually.<\/li>\n
  3. Collect and cluster the notes, using the list above only to fill gaps afterwards.<\/li>\n
  4. Pick the three to five causes with the highest combination of likelihood and cost.<\/li>\n
  5. Name one responsible person per item, set a due date, and book a check-in ahead of the release.<\/li>\n<\/ol>\n

    Ranking what you find<\/h2>\n

    Not every imagined failure deserves action. A simple, defensible approach is to ask two questions for each: how likely is it, and how bad would it be? Items that are likely and severe get immediate attention. Items that are unlikely but catastrophic often justify a safeguard or a rehearsed response. Items that are likely but trivial can be accepted. Document the reasoning so that later readers understand why a risk was left alone.<\/p>\n

    Common pitfalls<\/h2>\n
      \n
    • Holding the session too late.<\/strong> If the release date cannot move, findings arrive with nowhere to go.<\/li>\n
    • Letting seniority steer the list.<\/strong> Collect written notes first, discuss second.<\/li>\n
    • Treating it as a one-time event.<\/strong> Repeat it for significant releases and revisit the notes afterwards to see which items proved real.<\/li>\n
    • Skipping the owners.<\/strong> A concern without a name beside it rarely survives the week.<\/li>\n<\/ul>\n

      Closing note<\/h2>\n

      The appeal of the pre-mortem for engineering teams is its economy. It needs no tooling, takes an hour, and yields a short list of concrete actions. It also sets a healthy tone: acknowledging that releases can fail becomes a normal part of preparing for them. Run one before your next significant release, keep the notes, and compare them with what actually happens. Within a few cycles you will have a team-specific list of failure causes that is better than any generic list, including this one.<\/p>\n","protected":false},"excerpt":{"rendered":"

      Imagine the release has already failed. These eight causes show up again and again in engineering pre-mortems, with a way to test each while fixes are cheap.<\/p>\n","protected":false},"author":37,"featured_media":11804,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[147],"tags":[],"class_list":["post-11803","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-devops"],"yoast_head":"\n8 Reasons Your Release Could Fail, Found Before It Ships - Cotocus<\/title>\n<meta name=\"description\" content=\"Eight imagined causes of a failed software release, from mismatched environments to untested rollbacks, and how a pre-mortem helps you fix them early.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.cotocus.com\/blog\/eight-release-failure-reasons\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"8 Reasons Your Release Could Fail, Found Before It Ships - 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