After some tests on the Contabo (6 Cores) server, I found it has some performance inconsistency.

It's fast at first but slower after I run a test after. The memory and SSD speed is far slower than on the Hetzner server.

I choose NVME on Contabo but it is much slower from at first 600MB/s to ~200MB/s to 100MB/s.

The memory on Hetzner is 2-3 times faster than on the Contabo which my application relies on faster memory and a single-core CPU (Redis).

While the storage speed is not directly affected my application's performance. It makes it harder to migrate my dataset(38GB) to the new server.

Additionally, the interlink of the Contaba server is badly slow, ~200KB/s at the best, sometimes I can't even type on the ssh terminal even just from Bangkok to Singapore.

I will not move to Contabo for the reasons above.