The d3en.4xlarge is a storage-optimized AWS EC2 instance: 16 vCPU and 64 GiB of memory, 4.00 GiB per vCPU. In the name, "d" is dense local storage, "3" is the generation, "en" marks extended capacity and enhanced networking and "4xlarge" is the size within the d3en family. It runs on Intel Xeon Platinum 8259 (Cascade Lake) at 3.1 GHz, and AWS introduced it in December 2020. d3en is the current generation of the d family, so there is no newer AWS size to migrate to. Rackspace Spot's gp.vs1.2xlarge is a like-for-like substitute at 16 vCPU and 64 GiB, $2.10/hr on AWS in US East (N. Virginia), from $0.041/hr on Rackspace Spot.
Match qualityNo local disk
d3en.4xlarge comes with 8 × 13,980 GB NVMe SSD attached to the machine. Rackspace Spot nodes use network storage only, so that disk does not come with it.
If you were using the local disk as fast scratch space — temporary files, a local cache, an index — you will need a persistent volume or object storage instead, and both are slower to read. If it was just extra space you never depended on, nothing changes.