Can multiple instances of Alkaline run on multiple ports with the same data files?

Yes, you can run multiple instances of Alkaline on multiple ports for purposes such as load balancing for example. Alkaline loads all indexes in memory at startup and does not reload or use them during execution. Alkaline swap files are, of course, different. You should disable background indexing as writing index files from two different running Alkaline engines can produce unpredictable results.