First-in-First-Out

First-in-first-out is the dispatch policy that processes lots in the order they arrive to a queue without additional prioritization factors - it emphasizes fairness and simplicity over optimization of specific objectives.

What Is First-in-first-out?

• Definition: Queue discipline where earliest arrival receives service first.
• Operational Behavior: Minimizes overtaking and reduces risk of indefinite lot starvation.
• Implementation Ease: Simple to configure and explain across operations teams.
• Limitation Context: Ignores urgency, setup efficiency, due dates, and queue-time constraints.

Why First-in-first-out Matters

• Governance Simplicity: Useful baseline policy when process complexity is low.
• Fairness Control: Prevents arbitrary lot jumping in general queues.
• Predictable Behavior: Easier for operators to understand and audit.
• Optimization Tradeoff: Can underperform when mixed priorities and constraints are significant.
• Policy Benchmarking: Serves as reference point when evaluating advanced dispatch strategies.

How It Is Used in Practice

• Default Mode: Apply FIFO in non-critical queues with minimal setup dependency.
• Hybrid Overrides: Allow controlled exceptions for hot lots and queue-time risk lots.
• Performance Review: Compare FIFO outcomes against weighted and dynamic rules by objective.

First-in-first-out is a straightforward dispatch baseline for queue governance - while simple and fair, it often requires targeted overrides in fabs with tight deadlines and complex constraint interactions.