Benchmarks: What are the Typical SLAs in the Industry?

Setting an SLA is as much a marketing decision as it is an engineering one. Set it too low, and enterprise customers won't trust you. Set it too high, and you'll burn your engineering team out trying to maintain it. Here is where the market currently stands.

Cloud Infrastructure (IaaS)

The foundational layer of the internet sets the highest bar.

• AWS EC2 / Azure VMs: Typically 99.99%, but often contingent on using multiple Availability Zones (AZs). If you run a single instance, the guarantee drops to 99.5% or even less.
• Object Storage (S3): S3 Standard offers 99.9% availability SLA, though they design for 99.999999999% durability (not losing your data is different from being able to access it right this second).

SaaS & API Providers

As you move up the stack, SLAs tend to relax slightly due to the complexity of dependencies.

• Standard SaaS: 99.9% is the golden standard. Most B2B SaaS apps (Slack, Jira, etc.) target this. It strikes a balance between reliability and feature velocity.
• API Gateways (Apigee, Kong): Enterprise tiers often promise 99.99% for multi-region setups, acknowledging that they are critical path infrastructure for their customers.

The "99.999%" Unicorn

Five nines (5.26 minutes of downtime per year) is incredibly rare in general-purpose computing. It is usually reserved for:

• Telecommunications switches (the dial tone must always work).
• Pacemakers and life-critical medical devices.
• Mainframe systems in banking cores.

For most modern web applications, chasing five nines is a case of diminishing returns. The cost to go from four to five nines often exceeds the revenue lost during that extra 50 minutes of downtime.