- ECS runs on EC2（EC2 launch type)
- With EC2 launch type, tasks run on EC2 instances (that you manage), and those instances run an ECS agent.
- ECS runs on Fargate（Fargate launch type）
- With Fargate, your tasks run on Fargate-managed compute.
ECS on EC2 (EC2 launch type)
Pros
- Lower cost at scale (often cheaper for steady, long-running workloads; you can optimize instance utilization).
- More control & customization (instance types, GPUs, AMIs, daemon agents, deeper networking tweaks).
- More flexibility for advanced setups (special storage, sidecar agents, privileged containers in some cases).
Cons - More operational effort: you manage EC2 capacity, patching, upgrades, scaling, and instance failures.
- Capacity risk: if your EC2 cluster is full, tasks can get stuck in PENDING.
- More moving parts (Auto Scaling Groups, launch templates, AMI updates, etc.).
ECS on Fargate (Fargate launch type)
Pros
- Minimal ops / fastest setup: no EC2 provisioning, no patching, no cluster capacity planning.
- Easy scaling & reliability: tasks generally start without you worrying about available instances.
- Good security model: smaller attack surface since you don’t manage host OS.
Cons - Typically higher cost for always-on workloads (you pay per task CPU/memory; can be more expensive than optimized EC2).
- Less low-level control (can’t customize the underlying host, fewer tuning knobs).
- Some constraints (resource/feature limitations compared to full EC2 flexibility).