kdb+ is compressed columnar in memory on a single box with a very exotic language called Q. memsql is row-based in memory across n-machines using SQL.
kdb+ is also very fast for real-time time series analysis and signal generation. Seeing Morgan Stanley and Credit Suisse in the customer list made me wonder if memsql could become a competitor in the niche that kdb+ currently dominates?
Yes, if we note that there are core niches where nobody will replace kdb+ any time soon.