Why AWS EC2 T-Series Instances Are the Worst Choice for Most Computing Workloads ????

AWS T-series (T1, T2, T3, T3a, T4g) EC2 instances are popular for their low cost and burstable CPU performance, but they can be the worst choice in certain scenarios.

The CPU usage cap (or throttling after exceeding CPU credits) only applies to AWS burstable instances like T-series (T3, T3a, T4g) and some earlier-generation burstable instances (T2).

Other Instance Types – No CPU Cap

For non-burstable instances (M, C, R, etc.), there is no CPU cap, and you can use 100% of the allocated vCPUs without performance degradation.

Not only this, there are more reasons to avoid using them, Lets have a look into this below one by one.

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1. CPU Credit System = Unpredictable Performance

• T-series instances rely on CPU credits: They accumulate credits when idle and use them during high workloads. If credits run out, CPU performance drops significantly (throttling).
• Bad for: Workloads needing consistent CPU performance (databases, high-traffic web servers).
• Better Alternative: M5, C6i, or R5 instances for stable performance.

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2. Poor Performance for Sustained Workloads

• If your application has a steady high CPU demand, a T-series instance will throttle performance after exhausting credits.
• Bad for: ? Video encoding, CI/CD pipelines, analytics. ? Machine learning and big data workloads. ? Large-scale web applications.
• Better Alternative: C6i (compute-optimized) or M6i (general-purpose) instances.

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3. Limited Memory and Network Performance

• T-series instances have limited memory and network bandwidth.
• Bad for: ? High-memory applications (caching, large databases). ? High I/O applications (big data, distributed systems).
• Better Alternative: R6i (memory-optimized) or I4i (storage-optimized) instances.

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4. More Expensive for Long-Term Usage

• While T-series is cheaper upfront, if your app always runs at high CPU usage, you’ll pay more in the long run because: You may need to scale up sooner. Performance degradation may force instance upgrades.
• Better Alternative: Reserved M, C, or R instances for predictable workloads.

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5. Not Ideal for High Availability & Critical Workloads

• T-series instances don’t guarantee consistent performance, making them unreliable for mission-critical applications.
• Bad for: ? High-traffic websites. ? Enterprise production systems. ? Real-time processing applications.
• Better Alternative: M6i for general workloads, C6i for high CPU needs, R6i for high-memory apps.

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When is T-Series Good?

? Small, lightweight applications (e.g., dev/test environments). ? Low-traffic websites & APIs. ? Occasional workloads that don’t need continuous CPU.

When is T-Series the Worst Choice?

? Sustained CPU-intensive workloads (AI/ML, video processing, CI/CD).

? High-memory applications (databases, caching).

? Mission-critical, high-availability applications.

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Comparison Across Instance Families

Key Takeaways

• T-series = CPU credit system → Throttling happens when credits run out.
• M, C, R, X, I, etc. = No CPU cap → You can run them at 100% CPU continuously.
• If you need sustained CPU performance, avoid T-series and use M, C, or R instances.