# Messaging cost model established

Learner finished lesson 3 and read MDN Transferable objects plus Surma “Is postMessage slow?”. Treat as known: structured clone defaults and limits (no functions/DOM), transfer ownership / detached buffers, ~10–100 KiB cost framing as rule-of-thumb, patches/chunking/transfer before blaming workers, SharedArrayBuffer as advanced not default. Next ZPD: capability boundaries (what runs in a worker) and FE integration deal-breakers (tooling, DOM boundary, lifecycle, when not to use workers).