It uses 204-pin DDR3 SODIMM. It usually comes with 4GB, but you can swap that for 8GB (2x4GB) to give it a massive speed boost.
You love the aesthetic of early-2010s tech, need a cheap Linux machine (Ubuntu Mate runs like a dream on this), or want a dedicated DVD ripper. sony vaio pcg-71811m specs
Looking at the spec sheet today, the 320GB HDD is the biggest bottleneck. It uses 204-pin DDR3 SODIMM