Professional soldered RAM upgrades on modern thin laptops rarely succeed.

Low. Even for skilled technicians, the success rate for BGA rework on modern thin laptops is probably 50% at best, and I’d bet most are below that.

The problem isn’t the soldering skill itself. It’s that modern thin laptops use high-density multi-layer boards with very fine pitch BGA components (often the RAM is stacked on the CPU or soldered directly to the board with no margin for error). A rework station can heat the area, but the surrounding components — including the CPU — are not designed for that kind of thermal stress. Warping the board, lifting pads, or damaging the memory controller are common failures.

Even if the upgrade “works” initially, long-term reliability is suspect. Vias crack, solder balls develop micro fractures, and the laptop may start crashing months later. Most repair shops I trust flat out refuse to attempt it on anything newer than a 2018 MacBook or a business-class ThinkPad with known successful mods.

Buy the RAM configuration you need upfront. It’s not a user-serviceable part anymore, and pretending it is will cost you time, money, and a laptop that may never work right again.