AWS r7iz.12xlargevsAWS r7iz.4xlarge

r7iz.12xlarge pairs 48 vCPUs with 384GB of RAM at $4.4640/hr On-Demand (about $3214/mo at 24×7). r7iz.4xlarge pairs 16 vCPUs with 128GB at $1.4880/hr (~$1071/mo). r7iz.4xlarge is 67% cheaper per hour than r7iz.12xlarge ($2.9760/hr gap).

Because both instances are in the **r7iz 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: r7iz.12xlarge gives you 48 vCPUs and 384GB of RAM, r7iz.4xlarge gives you 16 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 r7iz.4xlarge delivers ~200% more single-thread Sysbench score per dollar (755 vs 2265 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 (82934 vs 27646) are what to weigh. Spot pricing flips many of these comparisons — when r7iz.12xlarge drops to $1.2894/hr and r7iz.4xlarge drops to $0.5730/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick r7iz.12xlarge when your workload is closer to memory-optimized (memory-bound work — in-memory databases, real-time analytics, large caches). Pick r7iz.4xlarge 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.