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Feature Flags & Toggles Marqeta Tech Talks

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Who? Manish Pandit Engineering

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Title? Feature Flags == Feature Toggles

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Feature Toggles Feature Toggles are a powerful technique, allowing teams to modify system behavior without changing code Source: https://martinfowler.com/articles/feature-toggles.html

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Meh.. We’ve all used them

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if (allowBackgroundRefresh) { initializeBackgroundRefresh(5, TimeUnit.SECONDS); }

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if (logLevel == LogLevel.DEBUG) { Console.log(“This should not be here”); }

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if (referenceNumber%2==0) { return shard1; } else return shard2;

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Deconstructing a Feature Toggle Toggle Configuration = on/off | env | user id(s) | geo | time | …. (Stored in config-file | database | env-var | in the code | FTaaS) Toggle Context = env | user id(s) | geo | time | logged-in-state | tenant-id | … Toggle Router = reads the toggle configuration + context to determine which toggle point to activate Toggle Point = execution path(s) for the toggle state(s)

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Think about it! Does the storage location of a Toggle Configuration affect when it can be toggled?

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Think about it! Does the storage location of a Toggle Configuration affect when it can be toggled? build | deploy | startup | runtime

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Types of Feature Toggles

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Release Toggles

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Release Toggles

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Release Toggles Decouple releases from deployments Referred a lot in the context of Continuous Integration (CI) Allow for large feature branches to be merged in master Long lived (based on how long the feature branches take - weeks? months?)

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Experiment Toggles

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A/B Testing

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Experiment Toggles Used to gather data to help pick the right feature (Mostly) used with end user interaction use cases (Can also be) used to tune system performance Short lived (weeks)

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Operational Toggles

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Operational Toggles Used to turn off features to control unknowns/unexpected Almost exclusively used in Production Short lived (days) till a baseline is established Can be lifetime (kill switches!) Help with graceful degradation

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Permission Toggles

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Permission Toggles Used to change behavior for a partial set of users May need to evaluate the user authorizations Canary, or incremental rollouts Beta, Early Adopters (or Early Winners as we call ‘em!) Can be very short (hours) or long (lifetime) lived

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Summary Source : https://martinfowler.com/articles/feature-toggles.html

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Pick the right place to store the toggle configuration (Ask the audience if they remember the storage options!)

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Do not name your toggles after pets, food, places..you get the point Follow a naming convention

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Use feature flags in moderation, use your best judgement

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Feature flags can turn into technical debt real quick - delete them once not in use. Hint : If a transient flag has been in the same state for a long time, it is not needed.

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Have an audit trail of any changes to Toggle configuration - treat it like sensitive data

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Let the experts do it for us!

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Launchdarkly Feature Management as a Service https://launchdarkly.com/

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Don't worry, these keys are duds by the time you’re seeing ‘em :)

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Resources Feature Toggles (aka Feature Flags) : https://martinfowler.com/articles/feature-toggles.html When Feature flags go bad - Edith Harbaugh : https://www.youtube.com/watch?v=28ZAoStv-Xw Getting Started with Feature Flags - #1 LaunchDarkly Feature Flags : https://www.youtube.com/watch?v=pwA_Ehp2SMY

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Fin.