Progressive JSON — overreacted

Progressive JSON is a streaming approach that sends data breadth-first using placeholders, allowing clients to process parts of the data tree as they arrive rather than waiting for the complete payload. Unlike traditional streaming JSON which sends data depth-first and creates malformed objects, progressive JSON uses placeholder references that get resolved progressively. This technique enables better performance by preventing slow operations from blocking everything that follows. React Server Components implement this pattern, streaming UI trees as progressive JSON while using Suspense boundaries to control when incomplete data is revealed to users.