They vastly exaggerate their popularity, helped by the lack of publicly available information. The number of quants writing q is dwarfed by those writing Python, Scala or even Slang.
First Derivatives’ revenue last FY was ~200m and their pre-tax profit is ~17m. To say that they are unaccountably popular on the Street is quite an overstatement.
The specialized time-series database lost much of its reason to exist when disk seek times went to zero. Nowadays you stage onto an SSD, and spool to rotating storage later, if at all.