CourseAI System Design: The Complete Course · Module 7: Model Layer · part 50 of 107
Part 50 · Module 7: Model Layer

Lesson 4: When the model changes under you

32 min read·
Module 7 · Lesson 4 · About 50 minutes · Needs: Module 4 lesson 3 (the model port) and Module 7 lesson 2 (shadow calls). No key and no model calls: every model here is a scripted stand-in

The situation

Week 7 at Northdesk. The gateway can choose between models, and Gareth asks what happens when one changes: a provider emails that Ask's model shuts down in sixty days, or changes the model behind the same name with no email at all. Helen wants both to be routine work, not incidents.

The running example is golden question G028: a Tallis Retail Group employee asks "How many days of annual leave do I get?". The answer is 30 days, citing t-tallis-d002; the superseded 2025 policy says 29.

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