Design a Reactive State System for an App Builder

Problem

Design the reactive state engine behind Retool: components with values that depend on each other via expressions, recomputing automatically.

Requirements

• Components expose state (table.selectedRow, input.value)
• Bindings reference other components
• Change propagates to dependents in order
• Detect and surface cycles

What evaluators look for

• Dependency graph + topological recompute
• Memoization and minimal recompute
• Safe expression evaluation/sandboxing

Extension

Add async data sources (queries) into the dependency graph.