SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a9bd3f3660f10a92df7c808864fc6184856248b877a528eccec8471993251a2' 
  AND token = '4XVv+jfBOOVVO7L88UT5ywbTke5TJQ0JZ5ZeRQ751ys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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