Prerequisites for Custom Domain Setup
Before configuring authentication and routing, ensure you have a registered domain in Route 53 and an active API Gateway stage. The most critical requirement is an SSL/TLS certificate. AWS Certificate Manager (ACM) certificates used with API Gateway must be issued in the us-east-1 (N. Virginia) region, regardless of where your API or Route 53 hosted zone resides. If you attempt to use a certificate from another region, the API Gateway console will reject it.
You also need a hosted zone in Route 53 that matches your domain name. For example, if your domain is api.example.com, you need a hosted zone for either api.example.com (for subdomains) or example.com (for apex domains). Ensure you have the necessary permissions to manage both Route 53 records and API Gateway configurations.
Provisioning the ACM Certificate
Navigate to the AWS Certificate Manager console and request a public certificate. Enter your domain names, such as api.example.com. You can choose DNS validation or email validation; DNS validation is preferred for automation and speed. Once requested, ACM will provide CNAME records that you must add to your Route 53 hosted zone. After adding these records, wait for ACM to verify ownership. The status should change to Issued before you proceed.
If you are managing infrastructure via code, refer to Behind the Scenes of AWS Terraform Provider for insights on automating certificate requests and validations within your IaC workflows. This ensures consistency across environments and reduces manual errors during deployment.
Configuring API Gateway Custom Domain
In the API Gateway console, select your API and navigate to the Custom Domains section. Click Create and enter your domain name. Select the ACM certificate you provisioned earlier from the dropdown menu. This step binds the certificate to the API Gateway endpoint, enabling TLS termination at the gateway level. Under Endpoint Type, choose Regional for most use cases, which associates the domain with a specific AWS region.
After creating the custom domain, note the Distribution Domain Name provided by API Gateway. This is typically a CloudFront distribution address ending in .cloudfront.net. You will need this value to configure your DNS records in Route 53. Without this domain name, you cannot correctly route traffic from your custom domain to the API Gateway.
Updating Route 53 DNS Records
Go to the Route 53 console and open your hosted zone. Create an A record alias that points to the API Gateway’s CloudFront distribution. Set the record type to Alias and select CloudFront as the target. Paste the distribution domain name into the field. This alias record ensures that Route 53 resolves your custom domain directly to the API Gateway without requiring additional IP lookups, reducing latency and avoiding TTL issues associated with standard A records.
If you encounter resolution delays after updating DNS records, check out Troubleshooting: Why is Taking too Long to Reflect Route 53 New Record with AWS SDK? to understand propagation factors and caching behaviors that might affect your setup.
Health Checks and Monitoring
Route 53 health checks monitor the availability of your API endpoints. Configure a health check targeting your custom domain URL (https://api.example.com). Set the failure threshold and interval according to your availability requirements. These health checks allow Route 53 to failover to secondary endpoints if your primary API becomes unhealthy, enhancing resilience.
Ensure your API returns appropriate HTTP status codes for health check probes. A 200 OK response indicates success, while other codes may trigger failures. Regularly review CloudWatch metrics for both API Gateway and Route 53 health checks to detect anomalies early. This proactive monitoring helps maintain service reliability and minimizes downtime for end-users.
Frequently Asked Questions
Why must the ACM certificate be in us-east-1?
API Gateway uses CloudFront under the hood for custom domains, and CloudFront only accepts ACM certificates from the us-east-1 region. Using a certificate from another region will result in an error when attempting to associate it with your custom domain.
Can I use a self-signed certificate for testing?
No, API Gateway requires a publicly trusted certificate issued by ACM or an external CA. Self-signed certificates are not supported for custom domains because browsers will reject them, causing connection errors for users.
What happens if Route 53 health checks fail?
If health checks fail, Route 53 can automatically route traffic away from the unhealthy endpoint, depending on your routing policy. This ensures that users are directed to healthy instances, maintaining service availability during outages.
How do I troubleshoot DNS resolution issues?
Verify that your Route 53 alias record points to the correct CloudFront distribution domain name. Check ACM certificate status to ensure it is issued and valid. Use tools like dig or nslookup to confirm that your domain resolves to the expected IP addresses.
Is there a cost associated with custom domains?
Yes, API Gateway charges for data processing and number of API calls. Additionally, Route 53 health checks incur costs based on the number of checks performed. CloudFront distribution fees also apply due to the underlying architecture of custom domains.