Comment by tannhaeuser

The domain-specific Prolog code bases you're going to create still can become large and represent a significant development effort. Prolog being an ISO standard with many conformant (or at least mostly conformant) implementations available and relatively strong mindshare and ecosystem compared to extremely niche "CP solver packages and OR-tools" (which one exactly?) significantly reduces project risks such as not being able to find experts, the system not meeting functional or performance requirements, or becoming obsolete down the road. The same cannot be said for some mythical "CP solver packages and OR-tools"; you've nowhere to go if your "CP solver packages and OR-tools" project fails. Optimization and scheduling/planning projects, by their nature, are somewhat experimental and need exploration. It would thus be very difficult to pick "CP solver packages and OR-tools" upfront.