AWS c5n.2xlargevsAWS c5n.4xlarge

c5n.2xlarge pairs 8 vCPUs with 21GB of RAM at $0.4320/hr On-Demand (about $311/mo at 24×7). c5n.4xlarge pairs 16 vCPUs with 42GB at $0.8640/hr (~$622/mo). c5n.2xlarge is 100% cheaper per hour than c5n.4xlarge ($0.4320/hr gap).

Because both instances are in the **c5n 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: c5n.2xlarge gives you 8 vCPUs and 21GB of RAM, c5n.4xlarge gives you 16 vCPUs and 42GB. 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 c5n.2xlarge delivers ~100% more single-thread Sysbench score per dollar (2688 vs 1344 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 (7081 vs 14271) are what to weigh. Spot pricing flips many of these comparisons — when c5n.2xlarge drops to $0.1667/hr and c5n.4xlarge drops to $0.3711/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c5n.2xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c5n.4xlarge 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.