Check signed sketches, recent windows, and exact range modes

Choose the operation contract or failure response implied by each structure. Check each choice against the runnable trace.

Lessons

• Count Sketch: estimate signed incident frequencies with row medians
• Exponential histograms: estimate failures in a recent event window
• Range-mode indexes: combine complete-block modes with fringe candidates

Design exercise

• Project: audit signed sketches, recent windows, and exact range modes
• Data Structures