I am working on SKU consolidation and my concern right now is if I have a cheaper option of SPDT switch with all the ratings same as SPST switch which is currently used. Can I replace it? Or does it depend on the particular application of the relay.
If all the ratings are the same, then yes you can use the SPDT in place of the SPST, you will just have an additional terminal on the package that is left floating that does not exist on the SPST. If there is already a PCB design utilizing the SPST, the PCB design may need to be updated for the new relay.
edit: Just to clarify, you used both the terms "switch" and "relay". My answer assumes you are talking about a relay.