Upstash QStash

What Upstash QStash is

Upstash QStash is a cloud-based serverless messaging and scheduling service that sits between an application and an API. It provides at-least-once delivery guarantees and automatic retries, and can schedule messages for later delivery; maximum delay depends on the plan. URL Groups publish messages to multiple endpoints in parallel, while queues deliver messages one at a time in enqueue order. Flow Control sets rate and parallelism limits, putting excess messages on a waitlist. Failed jobs can be retried or managed through a dead letter queue, and deduplication helps prevent duplicate delivery. QStash documents integrations for OpenAI-compatible providers and Anthropic, including batching chat completion requests and returning results to a callback. Requests include an HMAC-SHA256 signed JWT in the Upstash-Signature header for authenticity checks. The Free plan is free and includes 1,000 messages per day, 50 GB bandwidth, a 1 MB message limit and a seven-day maximum delay. Pay as You Go costs $1 a month, billed at $1 per 100K messages, with a 10 MB message limit and one-year maximum delay. Fixed plans and add-ons provide other listed limits and options.