When Should You Use Lambda Function URLs Or API Gateway?
A clear and concise breakdown on when to use which service for exposing API endpoints.
Did you know you can use AWS Lambda to create serverless function URL endpoints?
Most of you have read my slightly popular article on how to create Lambda function URLs without using API Gateway.
But when should you use Lambda function URLs and when is it more fitting to use API Gateway?
The answer, like always, depends on your architecture and use cases.
From a high level perspective, you would use Lambda function URLs for smaller and simpler applications that don’t require API management, while API Gateway provides highly flexible API management.
Let’s first compare both services, then explain when you should use which service in greater detail and finally explore a couple of real-life applications when you would use either service.
Pros and Cons
Lambda Function URL Pros
Rapid and easy to create and manage
Easy CORS configuration
Integrate with IAM
Lower latency (compared to using API Gateway)
Lambda Function URL Cons
Limited features
Basic security
No API management
API Gateway Pros
Advanced features
Caching, throttling, rate limiting, custom authorizers and request/response transformations
Robust security
Integrates with many other AWS services
API Gateway Cons
Higher costs for high-traffic use cases
More complex to setup and configure
Slightly higher latency due to additional layer between the client and Lambda
Now that we’ve seen the pros and cons of each service, let’s understand.
When To Use Lambda Function URLs
You should use Lambda function URLs when:
you need quick and simple APIs or for experimentations
you don’t need advanced features provided by API Gateway (like caching, throttling, rate limiting, custom authorizers and request/response transformations)
You want a lower cost option
When To Use API Gateway
You should use API Gateway when:
you need to manage multiple APIs with different endpoints and versions
you need the advanced features mentioned above
you need to integrate your API with various other AWS services
you require more API security options
Application Use Cases
Let’s explore an app use case where using Lambda function URLs would be more beneficial or fitting.
Imagine you have an internal data processing pipeline that needs to be triggered by an internal team to process documents and files uploaded to an S3 bucket.
The team uploads the files and a Lambda function URL is used to trigger the processing.
Here, the URL is used internally by the team only and only known to them. In this case, there’s no need for extensive security and API management.
Now, let’s modify our current example a little. If our data pipeline was more complex and is now used by multiple departments within the organization.
Say each department has different requirements for processing data and some departments require access to different stages of the pipeline.
Furthermore, they might need to ensure only authorized users can trigger certain parts of the pipeline. They also require logging and monitoring to track the usage and performance of the pipeline. They will likely also need to have throttling to prevent abuse and ensure a stable performance for the API.
In this case, as you may have guessed, API Gateway is much more fitting and even the only solution possible.
Conclusion
Choosing between AWS Lambda function URLs and API Gateway ultimately depends on the specific needs of your application.
Lambda function URLs are ideal for quick, simple APIs or experimentation, offering ease of use and lower costs without the advanced features of API Gateway. On the other hand, API Gateway excels in complex scenarios requiring robust API management, security, and integration with other AWS services.
By understanding the strengths and limitations of each service, you can make an informed decision that aligns with your architectural requirements and business goals. Whether you’re building a straightforward internal tool or a sophisticated multi-departmental system, AWS provides the flexibility to select the right tool for the job.
👋 My name is Uriel Bitton and I’m committed to helping you master AWS, Cloud Computing, and Serverless development. ☁️
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