An API Gateway API that keeps each browser connection open, so your backend can push messages at any time.
Think of it as: An open phone line instead of sending letters back and forth.
$connect, $disconnect and $default (any message no other route matches).@connections/{id}, which its role must allow with execute-api:ManageConnections.Normal HTTP is ask-then-answer. A WebSocket stays open in both directions. API Gateway’s WebSocket API holds the connections for you and gives each one a connection id. Your backend pushes a message by POSTing to the @connections/{id} URL, which IAM must allow (execute-api:ManageConnections).