Monitor AWS API Endpoints with CloudWatch Synthetic Canaries
Keeping a production API healthy requires evidence from outside the application stack. AWS CloudWatch Synthetic Canaries provide scheduled HTTP probes that test reachability, response codes and latency, then publish the results as CloudWatch metrics. This gives administrators a repeatable signal instead of relying on someone to open a browser and check a dashboard.
A basic health check confirms that an endpoint answers, but a scripted canary can go further. It can send a bearer token, request body or custom headers, assert that a JSON field contains the expected value and capture how long the request takes. Those capabilities support meaningful service-level validation rather than a simple uptime test.
Running the probe from AWS also removes the variability of an engineer’s home connection. The canary follows its configured schedule, produces a consistent history and continues while the team sleeps. That history becomes useful during incident analysis, especially when DNS, TLS certificates or a downstream dependency behave differently from the primary application.
Australian infrastructure teams must consider region placement, daylight saving and a spread of supported locations. Sydney and Melbourne sit in separate commercial AWS regions, while a home-lab test over a metropolitan NBN connection may mask the path experienced by customers. The monitoring design should reflect those conditions rather than a convenient test location.
Plan a meaningful API check
Begin with a low-risk request to a dedicated readiness endpoint, such as https://api.example.com.au/healthz. Decide the expected HTTP status code, acceptable latency and validation rules before creating the canary. A purpose-built health path should return minimal information, avoid database writes and remain safe to call every few minutes.
Next, choose the level of coverage. A public connectivity probe might use GET, while a deployment check can use POST with a JSON payload and a test identifier. Require authentication only where a meaningful assertion needs it, and store tokens in AWS Secrets Manager or Systems Manager Parameter Store rather than embedding them in canary code.
Configure the canary and its execution role
In the AWS console, open CloudWatch, select Synthetics, choose Canaries and create an API canary in the region that hosts the production API. Enter the URL, method, headers, parameters and request body, then add assertions for the response status and any critical payload values. Set a request timeout shorter than the API’s service-level objective so a slow dependency cannot hide until the canary itself times out.
Configure the schedule with a CloudWatch expression such as rate(5 minutes). Canaries run on UTC, so a schedule aligned to Australian business hours must account for AEST and AEDT changes. During daylight saving, an overnight shift can finish while the local clock has moved forward an hour; alerts should therefore state both UTC and the relevant Australian time zone.
Give the canary an execution role using the permissions described by the AWS-managed AmazonSyntheticsRole, adding narrowly scoped access for any secret or parameter the script retrieves. Keep the S3 artifact location dedicated, enable the required CloudWatch Logs permissions and apply tags for the endpoint, owner and environment. The tags make ownership visible during audits and automated infrastructure checks.
Connect probes to public and private APIs
A public API normally needs outbound HTTPS and reliable DNS resolution from the canary’s AWS location. Test the hostname independently because certificate expiry, an incorrect CNAME or a failed public lookup can produce the same red status as an application failure. The request log should capture enough detail to separate those cases without recording credentials.
For an API in a private VPC, attach the canary to subnets that can reach it and supply the necessary security groups. Add the Lambda VPC access permissions required by the setup. Those subnets need a route to the target, whether that is a NAT gateway for an internet-hosted application or VPC endpoints for AWS-hosted dependencies. Private DNS must also resolve correctly from the same network.
Build alarms around canary metrics
Create a CloudWatch alarm on the canary’s success percentage, and add a separate latency alarm where the endpoint has an agreed threshold. Use an evaluation window that reflects the service objective: a single transient failure may be tolerable, but repeated failures should page the team quickly. Configure missing data as breaching so a stopped or deleted canary cannot masquerade as a healthy service.
Publish alarm actions to an Amazon SNS topic wired into the on-call notification path. Include the endpoint, AWS region, failed assertion, canary version and both UTC and Australian local time in the message. An EventBridge rule can pass structured failure events to a Lambda function or AWS Systems Manager Automation runbook when automatic triage is warranted.
Exercise the notification path with a disposable canary before relying on it. Do not deliberately break a production API to test paging; use a controlled endpoint that returns a known failure. Record whether the alert reached the roster, included useful diagnostics and linked to the correct runbook. This makes the alarm an operational control rather than merely a visual indicator.
Run the monitor as an operational service
Treat the canary as a managed service rather than a one-off script. Infrastructure teams can define canaries in AWS CloudFormation, keeping the schedule, role and assertions alongside other managed resources. Review the configuration after API deployments, track versions when assertions change and retain execution logs for the required period. CloudTrail and CloudWatch Logs help establish when a check was altered or stopped, while S3 lifecycle rules prevent old artifacts from accumulating indefinitely.
Execution frequency and retention both affect cost. Each probe consumes Lambda invocations, metric writes and storage, so a five-minute check costs more over a year than an hourly one. Set coverage expectations around Australian business hours and assign failures during the arvo handover to the afternoon shift. A canary with no named owner quickly becomes background noise.
Regional probes can also expose path-specific faults. A Melbourne workload in ap-southeast-4 can be compared with a probe in ap-southeast-2 near Sydney to show whether failures follow the application or the network. The result is uptime visibility tied to customer experience, with clear ownership and an audit trail when something needs fixing.