add cohort targeting article

content/collections/experiment/en/cohort-targeting.md

@@ -0,0 +1,58 @@
+---
+id: 21a670fe-6939-4c52-919c-ff495b3109f3
+blueprint: experiment
+title: 'Cohort Targeting'
+landing: false
+exclude_from_sitemap: false
+updated_by: c0ecd457-5b72-4dc9-b683-18a736413d32
+updated_at: 1723477635
+---
+
+A cohort is a static or dynamic set of users defined in Amplitude. For experiment use cases, cohorts are particularly useful for advanced audience targeting. That said, cohorts are not always the best solution for targeting, so understanding how cohort targeting works with [local](./local-evaluation.md) vs [remote](./remote-evaluation.md) evaluation is important.
+
+Experiment cohort targeting currently only supports targeting **user** cohorts.
+
+## Remote evaluation
+
+When you target a cohort in a remote evaluation flag, the cohort is automatically synced to the *Amplitude Experiment* destination. For dynamic cohorts, this sync runs hourly by default. This means that dynamic cohorts targeted in remote evaluation are **not real-time**. For example, if you target a cohort of users who performed a `Sign Up` event, users will be targeted within an hour of performing the event--not immediately after.
+
+Cohorts targeted for remote evaluation may have a propagation delay on the initial sync or large change depending on the size of the difference. E.g. syncing a cohort of 10 million users for the first time will take some time to initially sync fully.
+
+**Use remote evaluation cohort targeting if...**
+
+- You are targeting users based on user behavior or properties which are not available in Experiment targeting segments.
+- You are ok with some targeting delay introduced by cohort sync intervals.
+
+**Don't use remote evaluation cohort targeting if...**
+
+- Users must be targeted in real-time.
+
+## Local evaluation
+
+Local evaluation flags that are deployed to up-to-date server-side SDKs can also target cohorts. When you target a cohort in a local evaluation flag, the cohort is automatically synced to the *Experiment Local Evaluation* destination. For dynamic cohorts, this sync runs hourly by default. This means that dynamic cohorts targeted in local evaluation are **not real-time**. For example, if you target a cohort of users who performed a `Sign Up` event, users will be targeted within an hour of performing the event--not immediately after.
+
+{{partial:admonition type="note"}}
+Local evaluation cohorts currently only sync **User IDs** to the SDKs. This means that in order to target cohorts in local evaluation flags, you **must** include a User ID in the user object passed to the evaluate function.
+{{/partial:admonition}}
+
+### SDK Support
+
+Server-side SDKs can target cohorts if configured to do so. Client-side SDKs do not currently support local evaluation cohort targeting.
+
+| SDK | Cohort Targeting | Version |
+| --- | --- | --- |
+| [Node.js](/docs/sdks/experiment-sdks/experiment-node-js) |  ✅ | `1.10.0+`  |
+| [Ruby](/docs/sdks/experiment-sdks/experiment-ruby) |  ✅ | `1.5.0+` |
+| [JVM](/docs/sdks/experiment-sdks/experiment-jvm) |  ✅ | `1.4.0+` |
+| [Go](/docs/sdks/experiment-sdks/experiment-go) |  ✅ | `1.6.0+` |
+| [Python](/docs/sdks/experiment-sdks/experiment-python) |  ✅ | `1.4.0+` |
+| [PHP](/docs/sdks/experiment-sdks/experiment-php) | ❌  | N/A |
+
+
+## Troubleshooting
+
+Troubleshooting cohort targeting can challenging due to the asynchronous nature of dynamic cohorts and cohort syncs in general. If you find that users that should be in the targeted cohort are not being targeted...
+
+- Check that the cohort has the required sync (*Amplitude Experiment* for remote evaluation, *Experiment Local Evaluation* for local evaluation).
+- Check that the cohort contains the expected user. If the user is contained in the current cohort, check the sync history of the cohort -- is it possible that the user was added to the cohort in a sync after the evaluation occurred?
+- Check that the user info passed to `fetch`/`evaluate` is correct.

content/collections/experiment/en/data-model.md

@@ -26,7 +26,7 @@ When developing a new feature with an experiment, you can create the experiment
 
 In Amplitude Experiment, a deployment serves a group of flags or experiments for use in an application. Each [project](#projects) has a deployment using the project API key as the deployment key, available by default. On creation, experiment deployments have an associated randomly generated **deployment key** which Experiment uses to identify the deployment and authorize requests to the evaluation servers.
 
-{{partial:admonition type="note" heading="Client vs. server deplpoyments"}}
+{{partial:admonition type="note" heading="Client vs. server deployments"}}
 Deployments are either client or server deployments. Use client-side deployments to initialize client-side SDKs, and server-side deployments to initialize server-side SDKs or authorize requests to the Evaluation API.
 {{/partial:admonition}}
 

content/collections/experiment/en/local-evaluation.md

@@ -34,7 +34,7 @@ Server-side SDKs can target cohorts if configured to do so. **Only User IDs can
 | SDK | Cohort Targeting | Version |
 | --- | --- | --- |
 | [Node.js](/docs/sdks/experiment-sdks/experiment-node-js) |  ✅ | `1.10.0+`  |
-| [Ruby](/docs/sdks/experiment-sdks/experiment-ruby) |  ✅ | `1.4.0+` |
+| [Ruby](/docs/sdks/experiment-sdks/experiment-ruby) |  ✅ | `1.5.0+` |
 | [JVM](/docs/sdks/experiment-sdks/experiment-jvm) |  ✅ | `1.4.0+` |
 | [Go](/docs/sdks/experiment-sdks/experiment-go) |  ✅ | `1.6.0+` |
 | [Python](/docs/sdks/experiment-sdks/experiment-python) |  ✅ | `1.4.0+` |

content/trees/collections/en/experiment.yaml

@@ -21,3 +21,5 @@ tree:
     entry: 99eb2927-ad52-424a-a04d-7e90a0ddfeb7
   -
     entry: 665e15c4-7194-4898-9cca-b58251cc79a2
+  -
+    entry: 21a670fe-6939-4c52-919c-ff495b3109f3