Code Smell 49 — Caches

Caches are sexy. They are a one-night stand. We need to avoid them in a long-term relationship.

Photo by Aimee Vogelsang on Unsplash

Problems

• Coupling
• Testability
• Cache invalidation.
• Maintainability
• Premature Optimization
• Erratic Behavior
• Lack of transparency
• Non-Deterministic behavior

Solutions

1. If you have a conclusive benchmark and are willing to pay for some coupling: Put an object in the middle.
2. Unit test all your invalidation scenarios. Experience shows we face them in an incremental way.
3. Look for a real world cache metaphor and model it.

Sample Code

Wrong

Right

Detection

This is a design smell.

It will be difficult to enforce by policy.

Tags

• Premature Optimization

Conclusion

Caches should be functional and intelligent.

In this way we can manage invalidation.

General purpose caches are suitable only for low level objects like operating systems, files and streams.

We shouldn’t cache domain objects.

This page is hosted on a cached website.

Relations

Code Smell 20 — Premature Optimization

More Info

What is Cache and Why do New Devs Struggle With It?

A Hitchhiker's Guide to Caching Patterns

There are only two hard things in Computer Science: cache invalidation and naming things.

Phil Karlton

Software Engineering Great Quotes

This article is part of the CodeSmell Series.

How to Find the Stinky parts of your Code