I guess I read a few things into the question. My experience is that a "record" is more often than not a series of rows in different tables, and the tricky question in these scenarios is making sure that updates either work or don't work in their entirety. This is what I was meant by the "this is what databases are for" line.

It is practically impossible to maintain a useful, enforceable lock on a record in a web application, given the lack of a persistent connection between the client (browser) and the back end. So you are usually left with two choices:

1. Last one in wins: given that the two users presumably have good reasons for modifying the record in question, let them figure it out if there is a conflict. As long as updates are atomic, consistent, blah, blah this works best.

2. Versioning: Every record has a version number associated with it and the database rejects updates with a version != to what is in there.

The real trick is to set yourself up so that you have a single-writer for any given piece of data in the common case and defer whatever locking is necessary optimistically to the database.