How to apply the TDD mindset to serverless

Testing is an integral part of software development, and serverless is no different.

Test Driven Development, or TDD, is long regarded as a leading practice in software development. And yet, one of the most misunderstood parts of Test-Driven Development (TDD) is the “Driven” part of the name. It’s not just about “writing tests before you write the code”. If your tests do not inform and drive your API design, then you’re not really doing TDD.

In this post, let’s look at how we can apply the TDD mindset to serverless and use our tests to drive the design of our serverless application.

When to use Step Functions vs. doing it all in a Lambda function

I’m a big fan of Step Functions, but it’s yet another AWS service you must learn and pay for.

It also introduces additional complexities. My application is harder to test; my business logic is split between configuration (ASL) and code; and I have new decision points, such as whether to use Express Workflows or Standard Workflows.

So it’s fair to ask, “Why should we even bother with Step Functions?”. Why not just do everything in code, inside a Lambda function?

Let’s break down the pros and cons and look at the trade-offs of each.

When to use API Gateway vs. Lambda Function URLs

“Lambdalith” is a monolithic approach to building serverless applications where a single Lambda function serves an entire API, instead of having one function per endpoint. It’s an increasingly popular approach and provides portability between Lambda and containers and lets you use familiar web frameworks.

Tools like the AWS Lambda Web Adapter have made this approach more accessible, and it also works well with Lambda Function URLs.

But don’t be too hasty to get rid of API Gateway just yet!

In this post, let’s look at the pros and cons of API Gateway vs. Lambda Function URLs, and let me explain why I still prefer API Gateway.

What’s the best way to migrate Cognito users to a new user pool?

The challenge with a Cognito User Pool migration is that the user password cannot be extracted from Cognito. This is a good thing. It shows that Cognito follows security best practices and does not store user passwords in plain text.

But it makes our lives more difficult during a Cognito User Pool migration.

In this post, let’s consider three approaches for migrating users to a new Cognito User Pool.

The one mistake everyone makes when using Kinesis with Lambda

AWS Kinesis and Lambda are a great combo for processing large amounts of data in real-time. However, there’s a common oversight that many developers make when integrating these two services. There are established best practices for configuring Lambda’s EventSourceMapping [1] for Kinesis: Configure an OnFailure destination for failed records. Enable BisectBatchOnFunctionError. Override MaximumRetryAttempts. Choose a …

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Amplify: how to share code without Lambda Layers or private NPM

Sharing code efficiently across different parts of an application can be challenging with AWS Lambda, especially when using Amplify. Today, I’ll walk you through a solution to this common problem, without relying on Lambda Layers or private NPM repositories. The Context In my previous post about Lambda Layers [1], I delved into its limitations, especially …

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How I built an affiliate tracking system in a weekend with serverless

Having taught thousands of students to build serverless applications via my online courses and workshops, I felt it was time to kick-start an affiliate program to boost sales. Affiliates would receive 50% of the revenue and get a 15% discount code for their audience. It feels like a good deal but I would need a …

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Static IP for Lambda: ingress, egress and bypassing the dreaded NAT Gateway

Many vendors require you to have a static IP address for your application. Such that all requests to their API must originate from an allow-list of IP addresses. This means we need to force egress traffic from our Lambda functions through a static IP address. Sometimes, they even mandate that you use a static IP …

Static IP for Lambda: ingress, egress and bypassing the dreaded NAT Gateway Read More »

What’s the most serverless way to wait for a slow HTTP response?

Every now and then you are faced with an awkward situation where you need to wait for a slow HTTP response and it can take more than 15 mins. Using Lambda is impractical because of the 15 mins timeout, and very cost ineffective because you will be paying for all that idle time by the millisecond.

If not Lambda, what’s the most serverless way for you to wait for a sloooow HTTP response?

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