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.