Design Principles

Crafting Software Architecture Diagrams

“Everything should be made as simple as possible, but not simpler” Albert Einstein

This timeless quote serves as the guiding philosophy for creating effective software architecture diagrams. The goal is to strike the perfect balance between simplicity and accuracy. Below are key principles to follow when designing architecture diagrams:

1. Start Simple, and Keep It Simple
2. Prioritize Clarity Over Completeness
3. Iterate and Add Details as the Design and Project Evolves

1. Start Simple, and Keep It Simple

Just like any well-crafted system, your diagram should begin with a simple foundation. That’s the topology, source, and sink topics. Focus on the critical path of stream processing, only add additional details when necessary, omit otherwise.

Crafting & maintaining good diagrams takes time and effort.

• prefer less/just enough over risk of fragmentation, outdated diagrams
• define a weight for a certain diagram; level of importance -> time to spend on
• include in user story acceptance criteria to update diagrams

2. Prioritize Clarity Over Completeness

The primary function of an architecture diagram is to convey the overall topology and flow of the system. Focus on the elements that are critical for the reader’s understanding. Include the key topic information, data types, data flow, context, and descriptions, but avoid cluttering the diagram with unnecessary details.

Just like with code coverage, perfection is not the goal. Your diagram should communicate the topology clearly, but it’s unnecessary (and often counterproductive if the diagram is too cluttered) to depict every detail.

This is particularly important for Kafka Streams Topology Designs. There’s a lot of complexity under the hood of the DSL that’s most likely not relevant to your design.

Here’s an example, three versions of the WordCountExample topology, with increasing levels of detail:

The RICH diagram shows certain technical details, hinting at Kafka Streams internals. But for this simple use-case, the BASIC diagram might be sufficient.

Caution

While the COMPLETE example (KSTD author speaking here 👋) is a valuable learning tool for understanding Kafka Streams, applying this level of detail to real-world applications can be overkill. It becomes error-prone, difficult to create, and even more challenging to maintain.

Furthermore, many of the details shown in the diagram simply are Kafka Streams defaults, valid for all stateful or aggregate operations. (Cached, logged RocksDB store; repartition & changelog topics; topic configs)

Now, imagine trying to model the ‘Ecommerce Product View’ example example with this much detail - prepare for potential mental overload 🤯.

3. Iterate and Add Details as the Design and Project Evolves

Software architecture is not static, and neither should your diagrams be. As your project evolves, so will your architecture.

Start with broad strokes and add finer details over time.

This iterative process ensures that your diagrams remain useful and up-to-date throughout the lifecycle of the project.

Closing Thoughts

The level of detail and the time invested in crafting your diagrams is entirely up to you, and should be tailored to each specific project or topology. Start by defining the complexity or “weight” of your diagram, begin with simple structures, and refine them iteratively.

Remember, it’s perfectly fine to brainstorm ideas through rough sketches in your meeting notes or even decide to forgo a diagram altogether. Not every diagram needs to be fully fleshed out or continuously maintained.