Another tricky issue is how to resolve REPL_SYNC vs REPL_ASYNC semantics. HttpSession repl is by default REPL_ASYNC; SFSB is REPL_SYNC. Let's say we have regions as a first level construct, so the SFSB part of the cache can have different rules from the http session part. Then a transaction modifies both parts of the cache. When the tx commits and we replicate the prepare() call, which semantics apply?