SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9b7b609e36751d932541c2ba6f2fc02828b8353ed4a3bcbcce24021a29a81f1b' 
  AND token = 'Cx68sJVusJw+lYBF8tuQrFV65tDHS25ujDoGIcChyiY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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