AWS i4i.12xlargevsAWS i4i.8xlarge

i4i.12xlarge pairs 48 vCPUs with 384GB of RAM at $4.1180/hr On-Demand (about $2965/mo at 24×7). i4i.8xlarge pairs 32 vCPUs with 256GB at $2.7460/hr (~$1977/mo). i4i.8xlarge is 33% cheaper per hour than i4i.12xlarge ($1.3720/hr gap).

Because both instances are in the **i4i family**, the only thing that changes between them is sizing — same silicon, same architecture (Intel Xeon (x86_64)), same burstable/sustained behavior. The choice is purely about how much capacity you actually need: i4i.12xlarge gives you 48 vCPUs and 384GB of RAM, i4i.8xlarge gives you 32 vCPUs and 256GB. AWS scales pricing close to linearly within a family, so picking the right size is mostly about right-sizing your workload, not getting a better deal per vCPU.

On raw price-per-performance, the two are i4i.8xlarge delivers ~50% more single-thread Sysbench score per dollar (722 vs 1084 points per $1/hr). That's the cleanest signal we have for "which one runs your workload faster per dollar," but it only matters if your workload is single-thread-bound; for parallel workloads the multi-core scores (74356 vs 49556) are what to weigh. Spot pricing flips many of these comparisons — when i4i.12xlarge drops to $1.2120/hr and i4i.8xlarge drops to $1.2277/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick i4i.12xlarge when your workload is closer to storage-optimized (NVMe SSD) (I/O-bound work needing low-latency NVMe local storage — NoSQL, search). Pick i4i.8xlarge when it's closer to storage-optimized (NVMe SSD) (I/O-bound work needing low-latency NVMe local storage — NoSQL, search). When neither side is obviously right, the cheaper hourly rate usually wins for fault-tolerant batch workloads, while the higher single-core score usually wins for latency-sensitive web traffic. The regional pricing tables linked from each instance page below show where each is currently cheapest — sometimes a >20% regional gap flips the comparison entirely.