Sort a file with huge volume of data given memory constraint

Question

Points:

• We process thousands of flat files in a day, concurrently.
• Memory constraint is a major issue.
• We use thread for each file process

Answer 1

If your restriction is only to not use an external database system, you could try an embedded database (e.g. Apache Derby). That way, you get all the advantages of a database without any external infrastructure dependencies.