ElixirConf 2023 - Tyler Young - Rebuilding the Plane While It’s Still Flying

Rebuilding a legacy system while minimizing downtime and data loss, Tyler Young shares practical lessons learned from his experience in adding new features to mature applications.

Key takeaways

Sometimes a feature needs to be added to a legacy system, and this can be challenging.
It’s better to understand why a rule exists before ignoring it.
When introducing a new feature, be prepared for issues and have a plan to address them.
In rebuilding the plane, keep the IDs the same to maintain data consistency.
It’s okay to have a little downtime during the process.
Use a map to provide context and make it easier to understand.
It’s not ideal to have multiple layers, but it can be lived with.
The scheme of migrations is important.
Indicator fields are necessary to understand the data migration process.
When migrating data, it’s good to have a way to reference old and new data structure.
It’s not hard to undo a migration, but it has to be done carefully.
Communities of Practice are important for sharing knowledge.
Lean on safe ectomigrations and excellent migrations to make the process easier.
The worst case is that a migration runs slowly and has errors.
Downtime can be a band-aid over not being able to make a migration atomic.
It’s good to have a way to add more context to a map.
Working on a feature while trying to fix bugs is challenging.
Don’t reintegrate old data structure into the new one.
It’s better to make small changes and test them than to make a big change and hope it works.
It’s good to have a plan for what to do when something goes wrong.
Communities of Practice are important for learning from others.
Keep the IDs the same to maintain data consistency.
It’s not hard to undo a migration, but it has to be done carefully.
Downtime can be a band-aid over not being able to make a migration atomic.
Don’t reintegrate old data structure into the new one.
It’s better to make small changes and test them than to make a big change and hope it works.

ElixirConf 2023 - Tyler Young - Rebuilding the Plane While It’s Still Flying

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