What is synapse problem?

Can you explain to me in detail what the "synapse problem" is in the context of cryptocurrency and finance? Is it related to blockchain technology, and if so, how does it affect the performance and security of digital transactions? Is it a recent discovery, or has it been a long-standing issue in the industry? Also, what solutions have been proposed to address this problem, and are there any ongoing efforts to develop new strategies to mitigate its effects?