Which AWS tool allows customers to forecast service usage and costs, plan instance reservations, and create custom alerts when usage or spending exceeds defined thresholds?

AWS Budgets allows you to set custom budgets to track your cost and usage, and receive alerts when actual or forecasted costs/usage exceed your defined thresholds. This enables proactive cost management and planning for instance reservations. Cost Explorer is primarily for visualizing and analyzing past and current costs, not setting alerts or forecasting against thresholds. The AWS Cost and Usage Report provides detailed billing data but doesn't offer forecasting or alerting capabilities. Reserved Instance reporting focuses specifically on RI utilization and savings, not overall budget management or custom alerts for general usage.