add apm dependencies

Author: mdbirnstiehl

solutions/observability/apps/dependencies.md

@@ -4,11 +4,48 @@ mapped_urls:
   - https://www.elastic.co/guide/en/serverless/current/observability-apm-dependencies.html
 ---
 
-# Dependencies
+# Dependencies [apm-dependencies]
 
-% What needs to be done: Align serverless/stateful
+APM agents collect details about external calls made from instrumented services. Sometimes, these external calls resolve into a downstream service that’s instrumented — in these cases, you can utilize [distributed tracing](../../../solutions/observability/apps/trace-sample-timeline.md#distributed-tracing) to drill down into problematic downstream services. Other times, though, it’s not possible to instrument a downstream dependency — like with a database or third-party service. **Dependencies** gives you a window into these uninstrumented, downstream dependencies.
 
-% Use migrated content from existing pages that map to this page:
+:::{image} ../../../images/observability-dependencies.png
+:alt: Dependencies view in the Applications UI
+:class: screenshot
+:::
 
-% - [ ] ./raw-migrated-files/observability-docs/observability/apm-dependencies.md
-% - [ ] ./raw-migrated-files/docs-content/serverless/observability-apm-dependencies.md
+Many application issues are caused by slow or unresponsive downstream dependencies. And because a single, slow dependency can significantly impact the end-user experience, it’s important to be able to quickly identify these problems and determine the root cause.
+
+Select a dependency to see detailed latency, throughput, and failed transaction rate metrics.
+
+:::{image} ../../../images/observability-dependencies-drilldown.png
+:alt: Dependencies drilldown view in the Applications UI
+:class: screenshot
+:::
+
+When viewing a dependency, consider your pattern of usage with that dependency. If your usage pattern *hasn’t* increased or decreased, but the experience has been negatively affected—either with an increase in latency or errors—there’s likely a problem with the dependency that needs to be addressed.
+
+If your usage pattern *has* changed, the dependency view can quickly show you whether that pattern change exists in all upstream services, or just a subset of your services. You might then start digging into traces coming from impacted services to determine why that pattern change has occurred.
+
+
+## Operations [dependencies-operations]
+
+::::{admonition} Dependency operations is in beta
+:class: important
+
+The Dependency operations functionality is in beta and is subject to change. The design and code is less mature than official generally available features and is being provided as-is with no warranties.
+
+::::
+
+**Dependency operations** provides a granular breakdown of the operations/queries a dependency is executing.
+
+:::{image} ../../../images/observability-operations.png
+:alt: operations view in the Applications UI
+:class: screenshot
+:::
+
+Selecting an operation displays the operation’s impact and performance trends over time, via key metrics like latency, throughput, and failed transaction rate. In addition, the [**Trace sample timeline**](../../../solutions/observability/apps/trace-sample-timeline.md) provides a visual drill-down into an end-to-end trace sample.
+
+:::{image} ../../../images/observability-operations-detail.png
+:alt: operations detail view in the Applications UI
+:class: screenshot
+:::