Though happy about Sun Microsystems Inc. ‘s second-quarter results, investors remained wary about the server and software maker’s ability to prosper under intensifying pressure from rivals.

The Santa Clara, Calif.-based company posted profit and sales that inched past Wall Street’s estimates Thursday, sending the stock price up 23 cents to $16.35 in after-hours trading. It had risen $1.30, or nearly 9 percent, to $16.12 during regular trading before the results were released.