SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '18b0dbfd6a2ff669d9b8b9643c58a143b5ff10400118d7967c2bf0030fd5f766' 
  AND token = '0wKfVoAZnHHuekAykOBYKxtaCqWUaJWysveV50BInpI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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