Programming

How to end-to-end test microservices across bounded contexts?

There is more than one way to test user journeys that span multiple bounded contexts. Your choice depends on organizational structure, team responsibilities, and the maturity of your testing practices.

Ultimately, every part of the user journey should be tested, whether it’s done piecemeal by individual teams or centrally by a QA/cross-functional team.

In this article, let’s look at several ways you can approach this problem, depending on if you have full-stack teams or specialised frontend and backend teams. We will look at trade-offs and whether it’s best to host other teams’ services in your environment, or use mock APIs, or delegate testing user journeys to a QA team and use a dedicated integration environment for testing.

All you need to know about caching for serverless applications

Caching is still important for serverless architectures. Just because AWS Lambda auto-scales by traffic, it doesn’t mean we can forget about caching. In this post, let’s break down by caching is still relevant for serverless and where we can apply caching in a serverless architecture. Caching is still VERY relevant. Yes, Lambda auto-scales by traffic. …

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AWS Lambda: how to share code between functions in a monorepo

A while back, a client asked me “how can I share business logic between services in a Node.js monorepo?”. The TL;DR of it is: Encapsulate the shared business logic into modules, and put them in a separate folder. In the Lambda handler functions, reference the shared modules using relative paths. Use webpack to resolve and …

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Step Functions as an ad-hoc scheduling mechanism

We previously discussed how you can implement an ad-hoc scheduling system using DynamoDB TTL as well as CloudWatch Events. And now, let’s see how you can implement the same system using AWS Step Functions and the pros and cons of this approach. As before, we will assess this approach using the following criteria: Precision: how …

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Using CloudWatch and Lambda to implement ad-hoc scheduling

A while back I wrote about using DynamoDB TTL to implement ad-hoc scheduling. It generated some healthy debate and a few of you have mentioned alternatives including using Step Functions. So let’s take a look at some of these alternatives, starting with the simplest – using a cron job. We will assess this approach using the …

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Making Terraform and Serverless framework work together

The Serverless Framework [1] is still the most popular deployment framework for serverless applications. It gives you a convenient abstraction over CloudFormation and some best practices out of the box: Filters out dev dependencies for Node.js function. Update deployment packages to S3, which lets you work around the default 50MB limit on deployment packages. Enforces …

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Understanding the scaling behaviour of DynamoDB OnDemand tables

Update 15/03/2019: Thanks to Zac Charles who pointed me to this new page in the DynamoDB docs. It explains how the OnDemand capacity mode works. Turns out you DON’T need to pre-warm a table. You just need to create the table with the desired peak throughput (Provisioned), and then change it to OnDemand. After you change the table to OnDemand …

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DynamoDB TTL as an ad-hoc scheduling mechanism

CloudWatch Events let you easily create cron jobs with Lambda. However, it’s not designed for running lots of ad-hoc tasks, each to be executed once, at a specific time. The default limit on CloudWatch Events is a lowly 100 rules per region per account. It’s a soft limit, so it’s possible to request a limit …

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