> For the complete documentation index, see [llms.txt](https://docs.serverlessapigateway.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.serverlessapigateway.com/glossary/m/middleware.md). # Middleware Software that acts as a bridge between an operating system or database and applications, especially on a network. Middleware is software that sits between the operating system and application layer, providing services and capabilities that applications use but do not implement themselves. In web development, the term more commonly refers to functions that process requests in a pipeline, executing logic before or after the main request handler. In web frameworks like Express.js, middleware functions have access to the request and response objects and can modify them, execute code, end the request-response cycle, or pass control to the next middleware in the chain. Common middleware tasks include parsing request bodies, handling CORS headers, logging, and session management. API gateways function as a form of middleware at the infrastructure level. They intercept API requests and apply processing logic -- such as authentication, rate limiting, request transformation, and response caching -- before forwarding requests to backend services. In serverless API gateways, middleware-like functionality is configured declaratively rather than written as code, allowing teams to compose request processing pipelines without managing server infrastructure. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://docs.serverlessapigateway.com/glossary/m/middleware.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.