SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a80a7d576dbad2a154e710a30109c5c94506b21867b8b495d6a06c946b35d55c' 
  AND token = 'n82iBzrz+57GzZPgU3H3N6kmgI7LiOZTugBAyFZfZvQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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