Size each service
Set CPU, RAM and replica count for each container. Keep an API running all day and run another workload only when needed.
Keep persistent data
Use volumes for data that must survive a container replacement. Runtime disk belongs to the running workload; it is not a replacement for a volume or a backup.
Check usage
Costs depend on resources, replicas and running time. Retained storage still counts when you stop a service. Try those settings in the simulator before deciding.