SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375c21fb92dfdec4e3879db63a1370c5e21178017abc9fb4a554ff0eabd63ac8' 
  AND token = 'qZpUYSXqK+CoyaBdLKOt8U0cTjVRIcG/m+yqPFtcsV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}