SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a3309f9363752616969756277014295fe3c3ab974fdad55ce1be75d85582353' 
  AND token = '5k2wYCq4EhkDFQkFhx1fa1JEKyh2sEMNFkYPx0hBjYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}