AWS c8i.12xlargevsAWS c8i-flex.12xlarge

c8i.12xlarge pairs 48 vCPUs with 96GB of RAM at $2.2490/hr On-Demand (about $1619/mo at 24×7). c8i-flex.12xlarge pairs 48 vCPUs with 96GB at $2.1365/hr (~$1538/mo). c8i-flex.12xlarge is 5% cheaper per hour than c8i.12xlarge ($0.1126/hr gap).

c8i.12xlarge (compute-optimized, Intel Xeon (x86_64)) and c8i-flex.12xlarge (compute-optimized, Intel Xeon (x86_64)) target different workload shapes. The vCPU:RAM ratios are different (48:96 vs 48:96), and depending on the architectures involved you may also see meaningful single-thread performance and per-hour-cost differences. This kind of cross-category comparison is most useful when you're early in the design phase and not yet sure whether your workload is CPU-bound, memory-bound, or balanced — once that's clear, the right pick is usually obvious.

Benchmark data for at least one of these instances is still being collected, so a direct performance-per-dollar comparison isn't possible yet. Sysbench scores are pending for c8i.12xlarge and 3322/84021 for c8i-flex.12xlarge. Check back as the benchmark queue completes — newer-generation instances typically score 10–30% higher on single-thread and 15–50% higher on multi-core vs the previous generation in the same series.

In practice, pick c8i.12xlarge when your workload is closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). Pick c8i-flex.12xlarge when it's closer to compute-optimized (CPU-bound work — batch processing, web servers under sustained load, game servers). 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.