AWS i3.4xlargevsAWS i3.8xlarge

i3.4xlarge pairs 16 vCPUs with 122GB of RAM at $1.2480/hr On-Demand (about $899/mo at 24×7). i3.8xlarge pairs 32 vCPUs with 244GB at $2.4960/hr (~$1797/mo). i3.4xlarge is 100% cheaper per hour than i3.8xlarge ($1.2480/hr gap).

Because both instances are in the **i3 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: i3.4xlarge gives you 16 vCPUs and 122GB of RAM, i3.8xlarge gives you 32 vCPUs and 244GB. 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 i3.4xlarge delivers ~104% more single-thread Sysbench score per dollar (728 vs 356 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 (10771 vs 21323) are what to weigh. Spot pricing flips many of these comparisons — when i3.4xlarge drops to $0.5908/hr and i3.8xlarge drops to $0.8886/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick i3.4xlarge when your workload is closer to storage-optimized (NVMe SSD) (I/O-bound work needing low-latency NVMe local storage — NoSQL, search). Pick i3.8xlarge 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.