The **Upstash QStash SDK** (`@upstash/qstash`) provides a TypeScript client for QStash, an HTTP‑based message queue and scheduler designed specifically for serverless and edge environments (e.g., AWS Lambda, Cloudflare Workers, Fastly Compute@Edge, Next.js edge runtime, Deno, etc.). It lets developers publish JSON payloads (including LLM requests) to a destination URL or URL group with at‑least‑once delivery guarantees, and offers utilities for verifying incoming signed webhook calls. The library is aimed at developers building serverless or edge applications who need a lightweight, stateless, HTTP‑only messaging solution.