Strategy Pattern

Mental model

The strategy pattern lets you swap an algorithm at runtime by hiding it behind a common interface. The caller does not know (or care) which version is used. Reach for it when "the same operation has many implementations" — pricing rules, sort orders, routing strategies.

How to study Strategy Pattern

Begin by restating the mental model in your own words, then connect it to a concrete system you have built or operated. Name the mechanism, the constraint it addresses, and the trade-off it introduces. Use Refactoring Guru — Strategy to check details, but close the source before writing your explanation. Retrieval is the learning step; rereading is only preparation.

Next, compare Strategy Pattern with the neighboring concepts in its roadmap. Ask what changes in correctness, latency, resource use, operability, and failure recovery. Complete Pluggable pricing strategies and preserve the command, input, output, and one failed attempt as evidence. Finish by explaining the idea without jargon to someone who has not studied the track.

Proof of understanding

• Explain the mechanism from first principles and identify the state it reads or changes.
• Give one situation where the concept is the right choice and one where it is not.
• Predict a realistic failure mode before running the drill, then compare the prediction with evidence.
• Connect the result to a roadmap or build artifact instead of treating the concept as isolated trivia.

Learn from primary sources

• Refactoring Guru — Strategy (doc)

Practice and explain it back

Review prompts

• Strategy pattern versus a switch statement — what concretely changes?

Build evidence

Use a roadmap capstone to turn this concept into working evidence.

Learning paths

• Runtime — what every runtime has to do
• The Software Engineering Landscape (2026)
• LLD Practice