The importance of EventStorming in serverless development
EventStorming is a great way to collaborate and to learn about business requirements, identify domain events, and shape the model before considering architecture and solution design. However, depending on the scale of the domain or product, the outcome of EventStorming could be high-level.
Say your organization is transforming the IT operations of its manufacturing divi‐ sion. The EventStorming exercise will bring together several domain experts, business stakeholders, enterprise and solution architects, engineering leads and engineers, product managers, UX designers, QA engineers, test specialists, etc. After a few days of collaboration, you identify various business process flows, domain events, model entities, and many bounded contexts, among other things. With clarity about the entire domain, you start assigning ownership—stream-aligned teams—to the bounded contexts.
These teams then delve into each bounded context to identify web applications, microservices, APIs, events, and architectural constructs to implement. While the artifacts from the domain-level EventStorming sessions form a base, serverless teams need more granular details. Hence, it is useful in serverless development if you employ EventStorming in two stages:
Domain-level EventStorming
According to Brandolini, this is the “Big Picture” EventStorming workshop aimed at identifying the business processes, domain events, commands, actors, aggregates, etc.
Development-level EventStorming
This is a more small-scale activity that involves an engineering team, its business stakeholders, the product manager, and UX designers. This is similar to what Brandolini calls “Design Level EventStorming.”
Here, the focus is on the bounded context and developments within it. The team identifies the internal process flows, local events, and separation of functionality and responsibilities. These become the early sketches for set-piece microservices, their interfaces, and event interactions. The outcome from the development-level EventStorming feeds into the solution design process (explained in Chapter 6) as engineers start thinking about the serverless architecture.
Let’s consider an example situation for development-level EventStorming:
Context: Figure 2-3 (in “Domain-first” on page 40) shows the breakdown of an ecommerce domain. A domain-level EventStorming workshop has identified the subdomains and bounded contexts. A stream-aligned team owns the user payments bounded context.
Use case: Due to customer demand and to prevent fraud, the stakeholders want to add a new feature where customers who call the customer support center to place orders over the phone can make their payments via a secure link emailed to them rather than providing the card number over the phone.
The proposed new feature only requires part of the ecommerce team to participate in a (development-level) EventStorming session. It is a small-scale activity within a bounded context with fewer participants.
Summary
You’ve just completed one of the most crucial chapters of this book on server‐ less development. The architectural thoughts, best practices, and recommendations you’ve learned here are essential whether you work as an independent consultant or part of a team in a big enterprise. Irrespective of the organization’s size, your ambition is to architect solutions to the strengths of serverless. Business requirements and problem domains can be complex and hard to comprehend, and it is the same in other fields and walks of life. You can observe and learn how people successfully solve non-software problems and apply those principles in your work.
Serverless architecture need not be a complex and tangled web of lines crisscrossing your entire organization. Your vision is to architect single-purpose, loosely coupled, distributed, and event-driven microservices as set pieces that are easier to conceive, develop, operate, observe, and evolve within the serverless technology ecosystem of your organization.
You will carry the learnings from these initial chapters with you as you go through the remainder of the book. You will begin to apply the architectural lessons in Chapter 5, which will teach you some core implementation patterns in serverless development. But first, the next chapter delves into one of the fundamental and critical topics in software development: security.