A public-safety CAD reporting fleet runs 24/7 on the same instance family for the next one to three years with predictable utilization. Which approach typically lowers cost versus pure On-Demand?
Select an answer to reveal the explanation.
Short Explanation
When the lights never turn off on those CAD boxes, AWS will cut the bill if you commit — Reserved Instances or Savings Plans are the multi-year discount handshake. Spot can vanish mid-shift, pure On-Demand leaves money on the table, and a Capacity Reservation alone is about holding space, not the same as the commitment discount story.
Full Explanation
A public-safety CAD reporting fleet that runs 24/7 on the same instance family for the next one to three years with predictable utilization typically lowers cost versus pure On-Demand by using Reserved Instances or Savings Plans commitment patterns. Steady-state civic systems that will not shrink dramatically are the classic candidates for commitment discounts: you trade flexibility for a lower effective compute rate while keeping the workload uninterrupted.
Always choosing Spot Instances is inappropriate when interruption would break the 24/7 reporting window. Leaving every instance On-Demand indefinitely despite stable multi-year utilization forgoes known savings. Purchasing a Capacity Reservation only holds capacity in an AZ; it does not automatically equal the deepest RI discount—capacity reservation and billing discounts are related but distinct concepts. The cost-saving commitment patterns are RIs or Savings Plans.
Exam caveat: Predictable steady state → RI/Savings Plans. Interruptible flexible → Spot. Need capacity guarantee in an AZ → Capacity Reservations (optionally combined with discounts). Do not assume a Capacity Reservation alone is the discount vehicle.
Operational check for public safety: measure baseline utilization for several weeks, choose RI or Compute/EC2 Savings Plans matching term and payment options finance allows, track coverage and utilization in Cost Explorer/Budgets, keep a small On-Demand/Spot buffer for spikes only where interruption is acceptable, and revisit commitments before renewal so decommissioned CAD nodes do not leave stranded spend.