SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '550ea5dd4617339a38b618710885943018f502354b89d8a084124b92e0b8e611' 
  AND token = 'nQvNedpmIOa2BkiAdvnOR+tBancrzvJGA8r+ZUkZJKk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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