AWS r6a.16xlargevsAWS r6a.8xlarge

r6a.16xlarge pairs 64 vCPUs with 512GB of RAM at $3.6288/hr On-Demand (about $2613/mo at 24×7). r6a.8xlarge pairs 32 vCPUs with 256GB at $1.8144/hr (~$1306/mo). r6a.8xlarge is 50% cheaper per hour than r6a.16xlarge ($1.8144/hr gap).

Because both instances are in the **r6a 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: r6a.16xlarge gives you 64 vCPUs and 512GB of RAM, r6a.8xlarge gives you 32 vCPUs and 256GB. 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 r6a.8xlarge delivers ~100% more single-thread Sysbench score per dollar (1124 vs 2248 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 (145295 vs 72642) are what to weigh. Spot pricing flips many of these comparisons — when r6a.16xlarge drops to $0.8006/hr and r6a.8xlarge drops to $0.6329/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick r6a.16xlarge when your workload is closer to memory-optimized (memory-bound work — in-memory databases, real-time analytics, large caches). Pick r6a.8xlarge when it's closer to memory-optimized (memory-bound work — in-memory databases, real-time analytics, large caches). 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.