AWS r8i.8xlargevsAWS r8ib.4xlarge

r8i.8xlarge pairs 32 vCPUs with 256GB of RAM at $2.2227/hr On-Demand (about $1600/mo at 24×7). r8ib.4xlarge pairs 16 vCPUs with 128GB at $1.6736/hr (~$1205/mo). r8ib.4xlarge is 25% cheaper per hour than r8i.8xlarge ($0.5491/hr gap).

Both are generation-8 memory-optimized instances, but they run on different silicon: **r8i.8xlarge** is Intel Xeon (x86_64), **r8ib.4xlarge** is Intel Xeon (x86_64). 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 r8ib.4xlarge delivers ~34% more single-thread Sysbench score per dollar (1493 vs 2007 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 (56009 vs 28283) are what to weigh. Spot pricing flips many of these comparisons — when r8i.8xlarge drops to $0.8480/hr and r8ib.4xlarge drops to $0.7508/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick r8i.8xlarge when your workload is closer to memory-optimized (memory-bound work — in-memory databases, real-time analytics, large caches). Pick r8ib.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.