AWS c8a.12xlargevsAWS c8a.16xlarge

c8a.12xlarge pairs 48 vCPUs with 96GB of RAM at $2.5865/hr On-Demand (about $1862/mo at 24×7). c8a.16xlarge pairs 64 vCPUs with 128GB at $3.4486/hr (~$2483/mo). c8a.12xlarge is 33% cheaper per hour than c8a.16xlarge ($0.8622/hr gap).

Because both instances are in the **c8a family**, the only thing that changes between them is sizing — same silicon, same architecture (AMD EPYC (x86_64)), same burstable/sustained behavior. The choice is purely about how much capacity you actually need: c8a.12xlarge gives you 48 vCPUs and 96GB of RAM, c8a.16xlarge gives you 64 vCPUs and 128GB. 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 c8a.12xlarge delivers ~33% more single-thread Sysbench score per dollar (2161 vs 1619 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 (263811 vs 351748) are what to weigh. Spot pricing flips many of these comparisons — when c8a.12xlarge drops to $1.0384/hr and c8a.16xlarge drops to $0.9364/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c8a.12xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c8a.16xlarge 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.