Oracle Visual Builder: Applications That Outlive Their First Release · Module 15 · Performance
Caching, and when it lies
Lesson 153 of 176 · 3 min
HOLDING DATA TO AVOID A CALL, and THE STALE VALUE SOMEBODY ACTED ON. Caching is the most effective performance fix and the only one in this module that can make an application WRONG rather than merely slow. THE TRADE IS EXPLICIT: YOU ARE EXCHANGING FRESHNESS FOR SPEED. Every cached value is a value that may have changed since you fetched it, and the question is never whether it can go stale — it is what happens when it does. WHICH IS WHY REFERENCE DATA IS THE SAFE CASE AND ALMOST THE ONLY ONE. A list of countries, statuses, categories. It changes rarely, everybody sees the same values, and being a day out is usually harmless — Lesson 3's repeated lookups, and the legitimate place to hold something. AND TRANSACTIONAL DATA IS THE DANGEROUS CASE. A balance, a status, an amount — anything somebody else can change while this user is…
The full lesson is part of the course
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