The key to fast queries at scale in real-time dashboards is ensuring that all dashboard queries operate on small, stable, and pre-aggregated data. This can be achieved through the use of incremental materialized views, refreshable materialized views, and in-memory dictionaries. These techniques allow for efficient updates and lookups without scanning the full dataset, resulting in significant speedups and memory reductions. By applying these optimizations to real-time dashboard scenarios, it's possible to achieve sustained performance at any scale, even with billions of JSON documents.