Simple definition
An HTTP persistent connection handles multiple requests over one transport connection to reduce connection overhead.
Purpose and use
A persistent HTTP connection keeps a transport available for multiple exchanges rather than closing it after every response.
How does it work?
A client can reuse compatible pooled connections. Concurrency and multiplexing depend on HTTP version and negotiated limits.
Example and verification
For performance analysis, separate connection setup, TLS negotiation and application processing for each request.
Points to watch
A persistent connection is not a user session and does not remove authentication checks. Devices can close it and establish a new connection.
In short
Persistence concerns exchange transport, distinct from content caching or retaining an application session.