Scalability, as today Bitcoin transactions are expensive and slow, what is a significant obstacle for performing micropayments and identify a unit behind this digital instant transactions. With average transaction size of 240 bytes, less than seven Bitcoin transactions are made each second. Comparing to 115 by PayPal and 2 thousand by VISA, which in theory can perform 56 thousand transactions per second, this number is very low. At the same time, an average speed of one transaction is 10 minutes with a maximum one-megabyte block size. Some Bitcoin enthusiasts and skeptics are afraid that in the future, the storage problem might also occur, as at very high transaction rates each block can be over half a gigabyte in size.