SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ad7638bc06e7cdc381b3d4a98caebb6c6dda41c395ce037ceb451ca4735ad28' 
  AND token = '616HHaR5Y8OAjWMBjVeetSRzdPtYlbES6RN8giTRbNM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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