Start with a customer path
A useful dependency map answers one question: what has to work for a customer to complete an important task? Start with a path such as signing in, checking out, or receiving a notification. Trace it from the browser or client through your own systems and every external service involved.
A complete company-wide diagram can wait. Mapping one important path usually exposes the dependencies that matter most.
Record operational context
For each dependency, record:
- the product or workflow it supports
- the owning team and an internal contact
- what customers experience when it fails
- whether requests can be queued, retried, or handled another way
- the vendor status page and support route
- the signals your team uses to confirm impact
Avoid treating a vendor status page as proof that your integration is healthy. Pair vendor status with an active check of your own endpoint or transaction where that is safe and practical.
Find dependencies in more than code
Application code is only one source. Review environment configuration, DNS records, identity providers, payment and messaging systems, build pipelines, package registries, support tools, and analytics. Ask product, support, finance, and operations teams what they need during a normal customer interaction.
Some dependencies are indirect. A checkout flow may call a fraud service that relies on another provider. You may not be able to map every downstream relationship, but you can record the vendor-facing boundary and the behavior your application sees when it fails.
Assign impact, not just a tier
A label such as critical is useful only when it changes the response. Write the expected effect in plain language: new users cannot sign in; existing sessions continue; payments can be accepted but confirmations are delayed. That description helps responders decide whether to fail over, disable a feature, queue work, or communicate with customers.
Keep the map close to the work
Maps become unreliable when updating them is a separate project. Link each critical path to its runbook. Add dependency review to architectural changes and incident follow-up. Give every entry an owner, and remove services that are no longer used.
ServiceAlert can keep selected vendor and first-party checks together in a monitored service. The map still belongs to your team; monitoring supplies current status and alerts when a recorded dependency changes.