SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '437ecc9ebb97b44febb3ebc962a195a44639e4418cac1a112b3d0185f1435811' 
  AND token = 'O57AIRxn9DIIHLbNj/xwU8+UwIt+xVjIIt1855sXuOE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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