AWS c7i.8xlargevsAWS c7i-flex.8xlarge

c7i.8xlarge pairs 32 vCPUs with 64GB of RAM at $1.4280/hr On-Demand (about $1028/mo at 24×7). c7i-flex.8xlarge pairs 32 vCPUs with 64GB at $1.3566/hr (~$977/mo). c7i-flex.8xlarge is 5% cheaper per hour than c7i.8xlarge ($0.0714/hr gap).

c7i.8xlarge (compute-optimized, Intel Xeon (x86_64)) and c7i-flex.8xlarge (compute-optimized, Intel Xeon (x86_64)) target different workload shapes. The vCPU:RAM ratios are different (32:64 vs 32:64), 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 c7i-flex.8xlarge delivers ~5% more single-thread Sysbench score per dollar (2300 vs 2412 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 (53822 vs 53516) are what to weigh. Spot pricing flips many of these comparisons — when c7i.8xlarge drops to $0.6481/hr and c7i-flex.8xlarge drops to $0.5897/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c7i.8xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c7i-flex.8xlarge 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.