SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'efc28631a7fb5e31ec6df22621226474a16764021f87e228756be6b266f80218' 
  AND token = 'GP3PO/mGWRWb3u3KTyAMj2dCHYoR3isZ+//dX3hEJm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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