https://speakerdeck.com/olarno 2026-06-05 08:07:25 -0400 When inheriting an unmaintained legacy Symfony application, the real question is not “how to migrate”, but rather “where to start without breaking everything”. In this talk, I share an honest retrospective of a Symfony migration carried out in production, on an aging application with limited documentation, few tests, and dependencies on components that are now obsolete. Through this journey, I offer a reading of the battlefield: risk areas, false good ideas, and decisions that seem obvious on paper… but turn out to be dangerous once confronted with real-world constraints. In particular, we will cover: - How to step back from an unmaintained legacy codebase and identify the real problems - The false good ideas we encountered during Symfony legacy migrations - Common mistakes observed in the field, and how to avoid or mitigate them - Small levers that make a big difference (order of actions, scope, tools, trade-offs) - Key lessons learned from this migration: what we would do again, and what we would clearly avoid This talk is aimed at developers working with inherited Symfony applications, often business-critical, who must move forward with limited visibility and very little room for error. The goal is not to promote a perfect or universal method, but to share a real, lived experience, and provide attendees with concrete reference points, clarity, and practical tips they can apply to their own migrations. When inheriting an unmaintained legacy Symfony application, the real question is not “how to migrate”, but rather “where to start without breaking everything”. In this talk, I share an honest retrospective of a Symfony migration carried out in production, on an aging application with limited documentation, few tests, and dependencies on components that are now obsolete. Through this journey, I offer a reading of the battlefield: risk areas, false good ideas, and decisions that seem obvious on paper… but turn out to be dangerous once confronted with real-world constraints. In particular, we will cover: - How to step back from an unmaintained legacy codebase and identify the real problems - The false good ideas we encountered during Symfony legacy migrations - Common mistakes observed in the field, and how to avoid or mitigate them - Small levers that make a big difference (order of actions, scope, tools, trade-offs) - Key lessons learned from this migration: what we would do again, and what we would clearly avoid This talk is aimed at developers working with inherited Symfony applications, often business-critical, who must move forward with limited visibility and very little room for error. The goal is not to promote a perfect or universal method, but to share a real, lived experience, and provide attendees with concrete reference points, clarity, and practical tips they can apply to their own migrations. Fri, 05 Jun 2026 00:00:00 -0400 https://speakerdeck.com/olarno/migration-legacy-symfony-in-production https://speakerdeck.com/olarno/migration-legacy-symfony-in-production