AWS m8i-flex.12xlargevsAWS m8i-flex.2xlarge

m8i-flex.12xlarge pairs 48 vCPUs with 192GB of RAM at $2.4132/hr On-Demand (about $1738/mo at 24×7). m8i-flex.2xlarge pairs 8 vCPUs with 32GB at $0.4022/hr (~$290/mo). m8i-flex.2xlarge is 83% cheaper per hour than m8i-flex.12xlarge ($2.0110/hr gap).

Because both instances are in the **m8i 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: m8i-flex.12xlarge gives you 48 vCPUs and 192GB of RAM, m8i-flex.2xlarge gives you 8 vCPUs and 32GB. 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 m8i-flex.2xlarge delivers ~500% more single-thread Sysbench score per dollar (1382 vs 8289 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 (84174 vs 14030) are what to weigh. Spot pricing flips many of these comparisons — when m8i-flex.12xlarge drops to $0.7497/hr and m8i-flex.2xlarge drops to $0.1385/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick m8i-flex.12xlarge when your workload is closer to general-purpose (balanced general-purpose workloads with a 1:4 vCPU-to-memory ratio). Pick m8i-flex.2xlarge 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.