AWS m8i.8xlargevsAWS m8i-flex.8xlarge

m8i.8xlarge pairs 32 vCPUs with 128GB of RAM at $1.6934/hr On-Demand (about $1219/mo at 24×7). m8i-flex.8xlarge pairs 32 vCPUs with 128GB at $1.6088/hr (~$1158/mo). m8i-flex.8xlarge is 5% cheaper per hour than m8i.8xlarge ($0.0846/hr gap).

m8i.8xlarge (general-purpose, Intel Xeon (x86_64)) and m8i-flex.8xlarge (general-purpose, Intel Xeon (x86_64)) target different workload shapes. The vCPU:RAM ratios are different (32:128 vs 32:128), and depending on the architectures involved you may also see meaningful single-thread performance and per-hour-cost differences. This kind of cross-category comparison is most useful when you're early in the design phase and not yet sure whether your workload is CPU-bound, memory-bound, or balanced — once that's clear, the right pick is usually obvious.

On raw price-per-performance, the two are m8i-flex.8xlarge delivers ~6% more single-thread Sysbench score per dollar (1963 vs 2075 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 (56016 vs 56644) are what to weigh. Spot pricing flips many of these comparisons — when m8i.8xlarge drops to $0.6760/hr and m8i-flex.8xlarge drops to $0.5922/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick m8i.8xlarge when your workload is closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). Pick m8i-flex.8xlarge when it's closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). 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.