0 extremely important or necessary for a company, activity, etc. to operate successfully -- (对公司或活动等)极其重要的,必须的
mission-critical applications/systems/software 极其关键的应用/系统/软件
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
再长的路,一步步也能走完,再短的路,不迈开双脚也无法到达。