Fast recovery characteristic — switching loss context
The 500 ns ceiling is conservative for a Schottky; typical turn-off times are well under 50 ns. For a 100 kHz PFC boost stage the switching loss in the diode is negligible compared to the conduction loss from the 920 mV Vf. The spec matters more if you are comparing against an ultrafast silicon diode in a replacement scenario — the Schottky wins on switching loss but loses on leakage at high temperature.
STMicroelectronics lists the STPS40170CT as Active. For a power-stage BOM that already qualifies this dual-Schottky footprint, there is no urgency to qualify a second source. The base product number STPS40170 covers the family; the CT suffix indicates the TO-220 package variant. If a future EOL were announced, the common-cathode TO-220 footprint is widely second-sourced across the industry — but that is a contingency, not a current need.