AWS r6g.12xlargevsAWS r6gd.4xlarge

r6g.12xlarge pairs 48 vCPUs with 384GB of RAM at $2.4192/hr On-Demand (about $1742/mo at 24×7). r6gd.4xlarge pairs 16 vCPUs with 128GB at $0.9216/hr (~$664/mo). r6gd.4xlarge is 62% cheaper per hour than r6g.12xlarge ($1.4976/hr gap).

Both are generation-6 memory-optimized instances, but they run on different silicon: **r6g.12xlarge** is AWS Graviton (ARM64), **r6gd.4xlarge** is AWS Graviton (ARM64). AMD variants (suffix `a`) are typically 10% cheaper than Intel siblings at comparable single-thread performance. Graviton variants (suffix `g`) are usually 20–40% cheaper but require ARM64-compatible binaries — most modern Linux stacks are fine, but verify any compiled extensions, native modules, or third-party binaries before migrating. Same vCPU/RAM ratio, same network performance class, different processor.

On raw price-per-performance, the two are r6gd.4xlarge delivers ~163% more single-thread Sysbench score per dollar (1159 vs 3045 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 (134325 vs 44551) are what to weigh. Spot pricing flips many of these comparisons — when r6g.12xlarge drops to $0.5329/hr and r6gd.4xlarge drops to $0.4185/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick r6g.12xlarge when your workload is closer to memory-optimized (memory-bound work — in-memory databases, real-time analytics, large caches). Pick r6gd.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.