SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4a9b4b4ef2bbbf295527937c989bff72fa8a1ece0175416b53a4be76e360481b' 
  AND token = 'XEvQdKm7IE1kELVZZxVW1dpNTJbvDzYGVU8NVcJnVqo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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