SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4f1926fe2d84e55c9a95788bc1637f50566636d999e260b7e950404761631502' 
  AND token = 'Qjhth2NGYFWOsFi13QmcbSV1yXjkLjwkghfFaqyQL8U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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