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Case Study #175 — 300 Software Failure Case Studies

AOL 1996 flat-rate pricing login congestion crisis

America Online's switch to unlimited, flat-rate internet access caused such a surge in simultaneous logins and prolonged sessions that millions of subscribers experienced constant busy signals and inability to connect for weeks; AOL later paid refunds under state attorney general settlements.

1996-12
When it happened
Retail / Technology
Sector
#175 of 300
Ranked by documented impact
01 — What Happened

The damage was public. The root cause was preventable.

America Online's switch to unlimited, flat-rate internet access caused such a surge in simultaneous logins and prolonged sessions that millions of subscribers experienced constant busy signals and inability to connect for weeks; AOL later paid refunds under state attorney general settlements.

Retail
Sector affected
1996-12
Date of the event
#175
Rank in the 300 Software Failure Case Studies
2
Distinct root-cause clauses identified below
02 — The Root Cause

What the software actually got wrong

AOL's network and modem-pool capacity, along with the software managing user sessions, had not been provisioned for a world where customers stayed connected far longer once usage-based charges were removed, and the company had not modeled the true scale of the resulting demand.

01Root Cause

AOL's network and modem-pool capacity, along with the software...

What Happened

AOL's network and modem-pool capacity, along with the software managing user sessions, had not been provisioned for a world where customers stayed connected far longer once usage-based charges were removed

How Requs AI Catches This

Requs AI Edge Case flags this exact pattern at the requirements and architecture stage — before a single line of code implementing it exists — so the assumption behind it gets challenged while it is still cheap to fix.

02Root Cause

The company had not modeled the true scale of...

What Happened

the company had not modeled the true scale of the resulting demand

How Requs AI Catches This

Requs AI Software FMEA traces this failure mode back to the system-level hazard it feeds, tagging it against the Common Defect Enumeration so it surfaces in review instead of in the field.

03 — How This Gets Caught Before It Happens

Beyond code coverage and "shall" testing

Root causes like this one rarely show up in code coverage or requirements-compliance testing, because nobody wrote a requirement anticipating the specific edge case that broke. Requs AI Edge Case and Requs AI Software FMEA are built to surface exactly this class of overlooked failure mode — before the software is written.

Requs AI Edge Case

Surfaces this before code exists

Identifies edge cases like this one at requirements and architecture time, using the Common Defect Enumeration to catalog failure patterns seen across hundreds of real-world software failures — including this one.

Requs AI Software FMEA

Connects the failure mode to the hazard

Traces this class of root cause directly to the system-level hazard it can produce, so a defect pattern like this one gets flagged during design review instead of after it ships.

Find the overlooked root causes before they ship.

Schedule a demonstration, or explore how Requs AI Edge Case and Software FMEA use the Common Defect Enumeration.