1 files changed, 235 insertions, 0 deletions
diff --git a/src/content/en/slide/2020/10/19/feature-flags.eslaides b/src/content/en/slide/2020/10/19/feature-flags.eslaides
new file mode 100644
index 0000000..3392e3e
--- /dev/null
+++ b/src/content/en/slide/2020/10/19/feature-flags.eslaides
@@ -0,0 +1,235 @@
+= Rollout, feature flag, experiment, operational toggle
+
+Different use cases for backend, frontend and mobile
+
+<<<
+
+== "Feature flags" tend to come up when talking about continuous deployment
+
+<<<
+
+[.lead]
+CI: continuous integration
+[.lead]
+CD: continuous delivery
+[.lead]
+CD: continuous deployment
+
+<<<
+
+== Types
+. rollout
+. feature flag
+. experiment
+. operational toggle
+
+// {favicon.svg}
+
+<<<
+
+== Rollout
+
+=== For *rolling out* a new version of software
+
+Short-lived using percentages
+
+// FIXME: links
+* a new deployment of kubernetes
+* new APK released to the Play Store
+
+<<<
+
+== Feature flag
+
+=== For turning a feature *on* or *off*
+
+Medium-lived using allow list, A/B test, percentage, app version, etc.
+
+* :new-chargeback-flow
+* :new-debit-card-activation-screen
+
+<<<
+
+== Experiment
+
+=== For analysing behaviour
+
+Medium-lived using allow list and A/B test
+
+* :debit-withdrawal-test
+
+<<<
+
+== Operational toggle
+
+=== For disabling features in #crash-like situations
+
+Long-lived using percentage
+
+* :bank-barcode-payment
+* :savings-bank-barcode-query-provider
+
+<<<
+
+[.lead]
+We know know about the types
+== But they have different relevance for backend, frontend and mobile
+
+<<<
+
+== backend
+. rollout: k8s blue/green, canary and [.line-through]#common-rollout# common-xp
+. feature flag: [.line-through]#common-rollout# common-xp and datasets
+. experiment: common-xp
+. operational toggle: [.line-through]#common-rollout# common-xp
+
+<<<
+
+== frontend
+. rollout: CDN and page refreshes
+. feature flag: percentages and maybe IPs (no :customer/id on the website)
+. experiment: via dynamic backend control
+. operational toggle: via dynamic backend control
+
+<<<
+
+== backend
+. rollout: app stores
+. feature flag: via dynamic backend control
+. experiment: via dynamic backend control
+. operational toggle: via dynamic backend control
+
+<<<
+
+[.lead]
+Key differentiator is
+== how much *control* we have over the environment
+
+<<<
+
+== backend
+=== full control
+// FIXME: emoji
+// 🎉
+
+<<<
+
+== frontend
+=== partial control
+We choose when to make a new version available
+
+<<<
+
+== mobile
+=== very limited control
+* app stores can restrict updates (worse for iOS)
+* customers still have to download new versions
+
+<<<
+
+== Costs
+* more complex code
+* compatibility with old app versions
+* nesting is exponential
+
+<<<
+
+== Benefits
+* dynamicity
+
+<<<
+
+== weighting costs × benefits
+=== The less control we have, the more we value dynamicity
+
+<<<
+
+== weighting costs × benefits
+* backend: sometimes worth the cost
+* frontend: almost always worth the cost
+* mobile: *always* worth the cost
+
+<<<
+
+== Best practices
+
+<<<
+
+== dynamic content > feature flag
+Always true for mobile, almost always for frontend
+
+<<<
+
+== Use :include-list for named groups
+Always true for backend, frontend and mobile
+
+----
+{:rules
+ #{{:types   :include-list
+    :content {:filename "debit-team-members.txt"}}}}
+
+----
+
+<<<
+
+== Always use :app-version
+Only for mobile
+
+----
+{:rules
+ #{{:types   :app-version
+    :content {:min-version #{{:platform :android
+                              :code     1000000}
+                             {:platform :ios
+                              :code     2000000}}}}}}
+
+----
+
+<<<
+
+== Extend [.line-through]#common-rollout# common-xp if required
+
+That's how :include-list, :app-version, etc. were born
+
+<<<
+
+== Beware of many nested feature flags
+True for backend, frontend and mobile
+
+<<<
+
+== Don't delete app-facing feature flags
+True for mobile
+
+<<<
+
+== Include a feature flag on the whiteboarding phase
+
+<<<
+
+== Include deleting/retiring the feature flag at the end
+
+<<<
+
+== Avoid renaming a feature flag
+Use :app-version with :min-version instead
+
+<<<
+
+== And most importantly...
+
+<<<
+
+== *Always* rely on a feature flag on the app
+Never do a hotfix, avoid expedited releases at all costs
+
+<<<
+
+== References
+// FIXME: links
+. "Feature Toggles (aka Feature Flags)", by Pete Hodgson
+. "Continuous integration vs. delivery vs. deployment", by Sten Pittet
+. Accelerate, by N. Forsgren, J. Humble and G. Kim
+. these slides: euandre.org/slide/
+. prose version of this presentation
+. view source