Side-by-side specifications of the Synology DS420j and DS420+, from official datasheets. Differences are highlighted.
| DS420j | DS420+ | |
| CPU | Realtek RTD1296 | Intel Celeron J4025 |
| Cores / threads | 4-core | 2 cores, 2 threads |
| RAM (base) | 1 GB DDR4 | 2 GB DDR4 |
| RAM (max) | 1 GB | 6 GB |
| Drive bays | 4 | 4 |
| Expandable to | 0 | 0 |
| M.2 slots | 0 | 2 |
| Network | 1 x 1GbE RJ-45 | 2x GbE RJ-45 |
| 10GbE | no | no |
| Max raw capacity | 64 TB | 64 TB |
| Hot-swap | no | yes |
| Form factor | desktop | desktop |
| Released | 2023 | 2020 |
Choose the DS420+ if you want noticeably more performance and headroom: it has a faster Intel CPU, 2 GB RAM with a much higher upgrade ceiling, and supports M.2 NVMe cache; it also has the same 4 bays but no 10GbE or expansion. Choose the DS420j only if you need the cheapest basic file backup/NAS box: it uses a much weaker ARM CPU, lower fixed RAM, and lacks M.2 cache and 10GbE, with no bay expansion on either model.