AWS c7i.2xlargevsAWS c7i-flex.large

c7i.2xlarge pairs 8 vCPUs with 16GB of RAM at $0.3570/hr On-Demand (about $257/mo at 24×7). c7i-flex.large pairs 2 vCPUs with 4GB at $0.0848/hr (~$61/mo). c7i-flex.large is 76% cheaper per hour than c7i.2xlarge ($0.2722/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.2xlarge gives you 8 vCPUs and 16GB of RAM, c7i-flex.large gives you 2 vCPUs and 4GB. 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.large delivers ~274% more single-thread Sysbench score per dollar (9199 vs 34403 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 (13466 vs 3005) are what to weigh. Spot pricing flips many of these comparisons — when c7i.2xlarge drops to $0.1592/hr and c7i-flex.large drops to $0.0304/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c7i.2xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c7i-flex.large 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.