SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '263aa7d576710a9687f10342521f5be54202b3fd58d1a17de3e0caf3cc46241c' 
  AND token = 'GxBVkh4LjHzYm6QATtiZw7GnkmOG+4LNwTmab0CAHj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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