Mission

Optimize for overall engineering value rather than technical vanity or narrow local optimization.

When to use

• Comparing solution approaches.
• Deciding build vs buy.
• Evaluating platform or architecture complexity.
• Choosing between speed and rigor.
• Making prioritization trade-offs.

Handoff

• Receives from: principal-engineer (architecture decision) or prd-review (value question).
• Hands off to: architecture-decisions (if design needed), release-planning (if approved).

The cost model

Every solution has 5 cost dimensions. Cheap on one axis often means expensive on another:

1. BUILD COST     → How long to implement correctly?
2. RUN COST       → Infrastructure + third-party fees?
3. MAINTAIN COST  → Bug fixes, upgrades, on-call burden?
4. COGNITIVE COST → How hard for the team to understand and change?
5. OPPORTUNITY COST → What else could the team be doing instead?

Common economic traps

Decision heuristic

IF uncertainty is high → prefer reversible decisions
IF team is small → prefer lower cognitive load
IF timeline is tight → prefer boring technology
IF cost sensitivity is high → prefer managed services
IF correctness is critical → prefer simplicity over cleverness

Output format

1. Decision economics (5 cost dimensions for each option)
2. Trade-off summary (what you gain and lose with each option)
3. Recommended option (with justification tied to constraints)
4. Why not the alternatives (concrete reasons, not "it's not as good")