SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a4d006bcd0923731a48209a97f4b135bbc833a4f1092a702ccf0e2942f303b1f' 
  AND token = 'FWzQE5Vdy902YJm6mKyMwcK4Q7Ipv4JjYPPyBOuK9nw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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