The Lord said “Assuredly I say to you that there are some standing here who will not taste death till they see the kingdom of God present with power” (Mark 9:11). How could that be, and which kingdom did He mean?
First we should understand the meaning of the word kingdom.
Apparently the person who asked the question had in mind the “Eternal Kingdom”, so he was puzzled about how some of the living at that time would live until they see the kingdom!!.
Of course, here He did not mean the “Eternal Kingdom”.
We should know that before the redemption, Satan was the prince of this world (John 14:30), and sin reigned, and by sin we die (Rom. 5:14&17) but by redemption God started to reign “the Lord reigned over a piece of wood”, bound Satan, saved the people from death and started His kingdom.
Then here it means the kingdom of God that spread by faith through the redemption of Christ “and the Lord added to the church daily those who were being saved” (Acts 2:47), so those joined the kingdom of God, the congregation of the believers.
The kingdom of God came with power, the power that came upon the disciples from above when they received the Holy Spirit. Few years, before St. Paul was martyred (year 67 AD); the kingdom of God had spread all over the known places of the world, and the people living then saw the kingdom of God coming with power.