I'm just thinking of how does blockchain gets delays from took 10-30 minutes or more since blockchain has an automated script.. Do they check each bitcoin transaction manually or something??
Mining (finding block that confirms transactions) is a random process. It takes 10 minutes on average, but it can be faster or take more time. The check whether the transactions are valid or not does not take that long.
This.
The whole mining aspect is actually all the miners performing a hashing algorithm to find a valid block that meets specified criteria. The number of hashes it takes to find a block is pretty much random, but is based upon a difficulty factor, or how hard it is to come up with the right hash. This difficulty factor (usually just called difficulty) will increase or decrease every 2016 blocks based upon how much hash-rate there is in the network. The whole idea is to keep block generation to 10 minutes on average, meaning 1 block (currently 25 bitcoins) is produced once every 10 minutes, or 6 times per hour.
Since there is some randomness involved, you will often notice fluctuations between new blocks. Sometimes they can be found less than a minute apart, and sometimes significant time, even an hour, can pass, before finding a new block. The thing to keep in mind is that the average generation over long periods of time still works out to 1 block every 10 minutes, but the block by block fluctuation can be less than or more than this.
