AWS r5dn.largevsAWS r5dn.xlarge

r5dn.large pairs 2 vCPUs with 16GB of RAM at $0.1670/hr On-Demand (about $120/mo at 24×7). r5dn.xlarge pairs 4 vCPUs with 32GB at $0.3340/hr (~$240/mo). r5dn.large is 100% cheaper per hour than r5dn.xlarge ($0.1670/hr gap).

Because both instances are in the **r5dn 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: r5dn.large gives you 2 vCPUs and 16GB of RAM, r5dn.xlarge gives you 4 vCPUs and 32GB. 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 r5dn.large delivers ~122% more single-thread Sysbench score per dollar (7000 vs 3156 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 (1752 vs 3139) are what to weigh. Spot pricing flips many of these comparisons — when r5dn.large drops to $0.0473/hr and r5dn.xlarge drops to $0.1877/hr, the cheap-per-hour winner can swing meaningfully.

In practice, pick r5dn.large when your workload is closer to memory-optimized (memory-bound work — in-memory databases, real-time analytics, large caches). Pick r5dn.xlarge 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.