Writing a Technical Design Document

Every project module since Module 12 has started with a design lesson — "Design the Requirement," "Design the Data Model," "Design the Payment Flow" — precisely because thinking through an approach before coding catches problems cheaply, on paper, rather than expensively, mid-implementation. A TDD formalizes this into a written artifact a team can actually review and discuss before any code exists.

# Technical Design: Automatic Case Escalation

## Problem
High-priority Cases open longer than 24 hours aren't being noticed
by support managers in time.

## Approach
A Scheduled Apex job (Module 38) runs hourly, querying open,
High-priority Cases older than 24 hours, and notifies the assigned
manager.

## Data Model
No new fields required — uses existing Case.Priority, Case.Status,
Case.CreatedDate.

## Edge Cases
- A Case reassigned mid-escalation-window (handled by re-checking
  the current OwnerId each run, not caching it).
- Bulk Case creation (handled — the query and notification logic
  are bulk-safe, Module 25).

## Testing Plan
Unit tests for the escalation query logic (Module 31); a scheduled-
job test confirming System.schedule fires correctly.

Every section maps directly onto habits this course has built: "Approach" (Module 26's requirement design), "Data Model" (Module 12), "Edge Cases" (Module 17), "Testing Plan" (Module 31) — a TDD isn't a new skill, it's these existing skills, written down in one shareable document.

A TDD is written for other developers and reviewers, not just yourself — the goal is that a teammate reading it can spot a missed edge case, a scaling concern, or a security gap (Module 28) before any code is written, when catching the problem is nearly free, rather than discovering it during code review or, worse, in production.