Cacheable Methods and Performance
By the end of this lesson, you'll be able to:
- Mark an @AuraEnabled method as cacheable=true
- Explain what the client-side cache actually stores and reuses
- Recognize when a method should NOT be marked cacheable
Prerequisites: "Returning Data to LWC: Wrapper Classes and DTOs"
Marking a method cacheable
@AuraEnabled(cacheable=true)
public static List<Account> getAccounts() {
return [SELECT Id, Name FROM Account];
}cacheable=true is the requirement referenced in Lesson 3 — it's what enables the wire service to work efficiently: the platform can serve a cached result immediately (showing the UI something right away) while it silently re-fetches fresh data in the background, rather than the user staring at a blank loading state every single time.
What actually gets cached
The client caches the result of a specific method call with specific parameters — calling searchAccountsByName('Acme') twice in a row can return the cached result instantly the second time, without a new server round-trip, while searchAccountsByName('Riverbend') is a different cached entry entirely, since the parameter differs.
When NOT to mark a method cacheable
// WRONG: this performs DML — it must never be cacheable
@AuraEnabled(cacheable=true)
public static void saveOpportunity(Opportunity opp) {
update opp; // compile error — cacheable methods cannot perform DML
}cacheable=true methods must be read-only — Apex actually enforces this at compile time, refusing to let a cacheable=true method perform any DML at all. This directly connects back to Lesson 3's rule of thumb: read/reactive methods can be cacheable; action-performing methods (like a save) must never be.
Exercise
As a comment, explain why Apex refuses to compile a cacheable=true method that performs DML.
Show hint
Think about what "cacheable" implies about the method never changing anything.
Cacheable Methods and Performance Quiz
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Summary
cacheable=true tells the platform this method's results can be safely cached on the client, avoiding a repeated server round-trip for the same request — but only genuinely fits read-only methods.