If there are use cases even now where a roll-your-own solution is best, imagine the 1980s. My first programming roles were in a mainframe shop with a major def

If there are use cases even now where a roll-your-own solution is best, imagine the 1980s. My first programming roles were in a mainframe shop with a major defense contractor, which had some brilliant mainframe system programmers over the years. Their major unclassified systems (payroll, shop order control, etc.) were internetworked with a homegrown real-time system, and they all had a home-grown disk access system (random and sequential) that was surreal in its speed and reliability, all coded in 370 assembler. On the business applications side, they had a thorough API that was callable from even COBOL programs. By the mid-1980s, upper management decided they had to "standardize" and began developing replacement systems using IBM's IMS. Performance was unusably bad. I left around that time to join the UNIX RDBMS world, so I don't know if they ever found a solution that could actually be rolled out. Working with the older stuff was actually fun because things just worked, and the customers of our legacy systems were really happy.