Look into using cookies to save user identifiers on the client during the initial login, and which can then be sent to the server on subsequent logins.
While you could save the actual password in a cookie, this is obviously a security risk. Instead, you can create some random string (a token) which is saved on the server DB together with some predetermined expiration timestamp, and returned to the client to be saved in a token, then on subsequent logins/calls you should check the token against the database.
You can probably make it even more secure by saving additional identification data (such as the client's IP - see Security/Get Session Attributes).
Keep in mind that the above is not hacker-proof, but might be good enough for your requirements.
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