Can you do this? Yes. Can you do it efficiently? I'm not sure.
It is unclear what the timeuuid you are using is.
You can reorganize it on
CREATE TABLE user_access (
user text,
access_time timestamp,
PRIMARY KEY (user_id, access_time)
);
SELECT COUNT(*)
FROM user_access
WHERE user_id = '101'
AND access_time > 'current unix timestamp - 3600'
AND access_time < 'current unix timestamp';
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