AWS c8a.16xlargevsAWS c8a.24xlarge

c8a.16xlarge pairs 64 vCPUs with 128GB of RAM at $3.4486/hr On-Demand (about $2483/mo at 24×7). c8a.24xlarge pairs 96 vCPUs with 192GB at $5.1730/hr (~$3725/mo). c8a.16xlarge is 50% cheaper per hour than c8a.24xlarge ($1.7243/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.16xlarge gives you 64 vCPUs and 128GB of RAM, c8a.24xlarge 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 c8a.16xlarge delivers ~50% more single-thread Sysbench score per dollar (1619 vs 1082 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 (351748 vs 484870) are what to weigh. Spot pricing flips many of these comparisons — when c8a.16xlarge drops to $0.9364/hr and c8a.24xlarge drops to $1.6859/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick c8a.16xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c8a.24xlarge 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.