Architecture & Sizing
AWS Intel Flex Comparison: C7i vs C7i-flex
Is the 5% discount on C7i-flex worth the CPU baseline constraints?
AWS introduced 'Flex' instances as a low-cost alternative to standard C7i and M7i. Learn how Flex instances allocate CPU and when they are safe for production.
1. Architectural & Silicon Specs Head-to-Head
Comparing underlying processor microarchitectures, memory ratios, and Nitro generation features using representative xlarge sizing.
c7ix86_64
C7I Compute Optimized
ProcessorIntel Xeon Scalable (Sapphire Rapids)
Clock Speed3.2 GHz
RAM / vCPU2.0 GiB/vCPU
Max Network50 Gbps
Max EBS IOPS240,000
AWS NitroSupported
Min Rate (c7i.xlarge)$0.1749/hr
Monthly Est.$127.71/mo
Cost per vCPU$0.0437/hr
Cost per GiB RAM$0.0219/hr
CoreMark Benchmark97,652
CoreMark / $558,203
Price Index100% of highest
Compute / $ Value100% (Leader)
c7i-flexx86_64
C7I-FLEX Compute Optimized
ProcessorIntel Xeon Scalable (Sapphire Rapids)
Clock Speed3.2 GHz
RAM / vCPU2.0 GiB/vCPU
Max NetworkUp to 25 Gbps
Max EBS IOPS80,000
AWS NitroSupported
Min Rate (c7i-flex.xlarge)$0.1662/hr
Monthly Est.$121.32/mo
Cost per vCPU$0.0415/hr
Cost per GiB RAM$0.0208/hr
CoreMark Benchmark81,045
CoreMark / $487,665
Price IndexLowest Cost
Save 5% vs most expensive
Compute / $ Value87% of leader
2. Side-by-Side Sizing & Pricing Matrix
Direct price and benchmark comparison across matching instance tiers in the lowest-cost region. Lowest hourly cost in each row is highlighted in green.
| Size Tier | vCPU | Memory | c7iLinux Rate | c7i-flexLinux Rate |
|---|---|---|---|---|
| .large | 2 | 4 GB | ||
| .xlarge | 4 | 8 GB | ||
| .2xlarge | 8 | 16 GB | ||
| .4xlarge | 16 | 32 GB | ||
| .8xlarge | 32 | 64 GB | ||
| .12xlarge | 48 | 96 GB | ||
| .16xlarge | 64 | 128 GB | ||
| .24xlarge | 96 | 192 GB | — | |
| .48xlarge | 192 | 384 GB | — |
3. Workload Decision Framework
Clear, actionable rules on when each family wins based on workload profile, runtime language, and licensing boundaries.
Recommended:C7i-flex
When: Typical web servers and API fleets with variable, bursty traffic
Why: Instant 5% cost reduction with no code changes and strong average performance.
Recommended:C7i
When: Continuous batch jobs, scientific computing, or predictable 100% CPU loads
Why: Full sustained performance without hypervisor CPU management throttling.
5. Related Architecture Comparisons
Explore adjacent generational comparisons and silicon trade-offs.