AWS m8i-flex.xlargevsAWS m8i.xlarge

m8i-flex.xlarge pairs 4 vCPUs with 16GB of RAM at $0.2011/hr On-Demand (about $145/mo at 24×7). m8i.xlarge pairs 4 vCPUs with 16GB at $0.2117/hr (~$152/mo). m8i-flex.xlarge is 5% cheaper per hour than m8i.xlarge ($0.0106/hr gap).

m8i-flex.xlarge (general-purpose, Intel Xeon (x86_64)) and m8i.xlarge (general-purpose, Intel Xeon (x86_64)) target different workload shapes. The vCPU:RAM ratios are different (4:16 vs 4:16), 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.xlarge delivers ~5% more single-thread Sysbench score per dollar (16574 vs 15712 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 (7006 vs 6985) are what to weigh. Spot pricing flips many of these comparisons — when m8i-flex.xlarge drops to $0.0622/hr and m8i.xlarge drops to $0.0910/hr, the cheap-per-hour winner can swing meaningfully.

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