Instances›AWS EC2›r8i-flex›r8i-flex.16xlarge
Compute
vCPUs64
Memory512 GiB
Mem / vCPU8.00 GiB
ProcessorXeon Scalable
Clock speed3.9 GHz
Architecturex86_64
Storage
TypeEBS only
Bandwidth20,000 Mbps
Throughput2500 MB/s
IOPS80,000
Networking
PerformanceUp to 30 Gigabit
Max ENIs16
IPv6Yes
GPUNone
Family sizes
r8i-flex.large2 vCPU · 16 GiB
r8i-flex.xlarge4 vCPU · 32 GiB
r8i-flex.2xlarge8 vCPU · 64 GiB
r8i-flex.4xlarge16 vCPU · 128 GiB
r8i-flex.8xlarge32 vCPU · 256 GiB
r8i-flex.12xlarge48 vCPU · 384 GiB
r8i-flex.16xlarge64 vCPU · 512 GiB
r8i-flex.16xlarge

The r8i-flex.16xlarge pairs 64 vCPU with 512 GiB of RAM, the 8.00 GiB-per-vCPU ratio that marks a memory-optimized instance. It runs on Intel Xeon Scalable (Granite Rapids) at 3.9 GHz, and AWS introduced it in August 2025. Spot's node ladder tops out below this size, so r8i-flex.16xlarge becomes 4 × mh.vs1.2xlarge (64 vCPU, 512 GiB combined), $4.22/hr on AWS in US East (N. Virginia), from $0.084/hr on Rackspace Spot. Spot delivers compute as managed Kubernetes, so a node pool of that size is the native shape of the answer rather than a workaround — provided the workload scales horizontally.

Match qualityScale-out match

r8i-flex.16xlarge gives you 64 vCPU and 512 GiB in a single machine. The largest comparable Spot node, mh.vs1.2xlarge, is 16 vCPU and 128 GiB, so the equivalent here is 4 nodes rather than one.

Spot runs as managed Kubernetes, so a 4-node pool is the normal way to run things rather than a workaround. If your workload already sits behind a load balancer, a queue or a scheduler, it spreads across them without changes. If it needs all 64 cores and 512 GiB in one process, it does not.

Pricing by region
1 hr
RegionAWS on-demandAWS Spot1-yr Reserved3-yr ReservedRackspace SpotYou save
US East, N. Virginia$4.223$1.094$0.084
$4.139 savings
US Central, Chicagono AWS region$0.084
US Central, Dallasno AWS region$0.524
Hong Kong$0.084
Sydney, Australia$5.061$1.763$0.084
$4.977 savings
London, UK$4.960$1.468$0.524
$4.436 savings
US West, San Jose$4.692$1.217$0.008
$4.684 savings
US Central, Dallas 2no AWS region$0.968
When to use it
Good for
  • ●Database instances that keep the working set in RAM
  • ●Graph and search workloads with large indexes
  • ●In-memory caches such as Redis and Memcached
  • ●Workloads that fit inside 512 GiB of RAM
  • ●Parallel work that can occupy 64 vCPU
  • ●Network-heavy services — AWS rates this size at Up to 30 Gigabit
  • ●Anything that shards cleanly across 4 nodes, which is how it maps onto Rackspace Spot
Avoid if
  • ●The working set needs more than 512 GiB of RAM
  • ●Local NVMe or instance-store disk is a hard requirement
  • ●GPU or FPGA acceleration is needed
  • ●CPU-bound work. You are paying for memory this workload will not use.
  • ●More than 8.00 GiB of RAM per vCPU is needed — that ratio is fixed for the whole family
  • ●The work is single-threaded. Most of these 64 vCPU would sit idle.
$3,083/mo on AWS on-demand against $61/mo on Rackspace Spot for the 4-node equivalent — market-priced, not list-priced.
  • Spot sells spare capacity at market prices. It is the cheapest compute on the internet.
  • Prices are set by supply and demand. You pay what the market decides.
  • Compute is delivered as fully managed Kubernetes. All infrastructure is taken care of.
  • Egress costs $0.01/GB after the free allowance. AWS charges $0.09/GB.
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