SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d828bafa45dd93301a5a368e6bc41806ea49367b392dcfc4ed91ece11a18f2' 
  AND token = 'XlnlQhPmqAa//4Z6kycqtMdTwmYiDpQUA6o/xgtFM/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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