AWS c7i-flex.16xlargevsAWS c7i.metal-24xl

c7i-flex.16xlarge pairs 64 vCPUs with 128GB of RAM at $2.7132/hr On-Demand (about $1954/mo at 24×7). c7i.metal-24xl pairs 96 vCPUs with 192GB at $4.2840/hr (~$3084/mo). c7i-flex.16xlarge is 58% cheaper per hour than c7i.metal-24xl ($1.5708/hr gap).

Because both instances are in the **c7i 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: c7i-flex.16xlarge gives you 64 vCPUs and 128GB of RAM, c7i.metal-24xl gives you 96 vCPUs and 192GB. 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 c7i-flex.16xlarge delivers ~55% more single-thread Sysbench score per dollar (1194 vs 771 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 (90675 vs 136939) are what to weigh. Spot pricing flips many of these comparisons — when c7i-flex.16xlarge drops to $0.7791/hr and c7i.metal-24xl drops to $1.1900/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c7i-flex.16xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c7i.metal-24xl when it's closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). 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.