What does the 503 status mean when working with a web service?

HTTP status 503 means "Service Unavailable" — the service is unavailable. This indicates that the server is temporarily unable to handle the request due to overload or maintenance.

Main reasons for 503:

• The server is overloaded and cannot handle the load.
• Maintenance work is being carried out on the server.
• Temporary failures in infrastructure (e.g., database is unavailable).

For the user, this is a signal that the problem is temporary, and it is advisable to retry the request later. The server response often includes a Retry-After header, which recommends the waiting time before retrying.