SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '906044edf83051cecade391a6b372cac078e210adf0d894e9edb11b9bcbac276' 
  AND token = 'SXO3gEnlqCuNf6kDQoBqNTimLDARYJNrd5ZG9qYc+eM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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