What is a single point of failure?
One component, person, supplier or location whose failure stops everything that depends on it.
One thing that brings down the rest.
A single point of failure (SPOF) is any part of a system, process or organisation that has no backup or alternative, so that if it fails the whole service stops. It can be technical, such as a single server or network link, but also a single supplier, a single site, a single approver or one person who holds critical knowledge.
Finding and treating single points of failure is a core part of business continuity, IT resilience and operational resilience.
Common single points of failure.
Technology
One server, database, firewall, DNS provider, certificate or network link.
Power and cooling
A single utility feed, generator, transformer, UPS or chiller loop.
Location
One office, data centre, factory or warehouse, or one city or region.
Suppliers
A sole-source supplier, one logistics route, one cloud provider or one software vendor.
People
A key person, a unique skill, or one approver who must sign off every action.
Information
A single copy of data, one spreadsheet, or knowledge that is not written down.
Processes
A manual step that only one team can do, or a process with no workaround.
Geography
One port, canal, bridge, pipeline or border crossing.
How to identify single points of failure.
Start with critical services
Use the business impact analysis to list the services that matter most and their recovery targets.
Map dependencies
For each service, list the people, sites, technology, suppliers and data it needs, down to the second and third level.
Ask what happens if it is gone
For each dependency, ask: if this failed for a day, or a week, what would we do?
Use structured methods
Techniques such as failure mode and effects analysis (FMEA) or fault tree analysis can help in technical settings.
Check hidden sharing
Look for shared cables, power, software, accounts, suppliers or locations behind apparently separate services.
Review after incidents
Real events and exercises often show single points of failure that desk reviews missed.
What to do about a single point of failure.
Add redundancy
Add a spare or alternative. See What is Redundancy?.
Diversify
Use a second supplier, route, provider or location.
Build workarounds
Prepare manual or alternative ways to deliver the service for a limited time.
Cross-train
Share skills, name deputies and document how things are done.
Contract and plan
Include recovery commitments in supplier contracts and agree exit plans.
Monitor
Detect failure quickly with alarms and checks, and set escalation routes.
Accept knowingly
Where treatment is not worth the cost, record the risk and agree it with senior management.
Exercise
Test what happens when a single point fails, and learn from it.
When one thing took down many.
March 2025, Heathrow
A fire at one electrical substation was reported to have closed a major airport for most of a day, with flights cancelled or diverted across the world.
March 2021, Suez Canal
One grounded ship blocked a canal that carries a large share of world trade for about a week.
March 2024, Baltimore
The collapse of one bridge closed a major port to most traffic for weeks.
July 2024, CrowdStrike
One faulty software update crashed millions of Windows devices, disrupting airlines, banks and hospitals.
October 2021, Facebook
A single configuration change took several services offline for hours.
Key-person risk
Small and large organisations alike can be stopped when the one person who knows a system, password or process is unavailable.
Examples are drawn from public reports and are simplified. Check the original reports for details.
Single point of failure questions.
Can we remove every single point of failure?
Is a key person a single point of failure?
What is the difference between a single point of failure and concentration risk?
Talk to ADVOX about dependency mapping and resilience.
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Related reading: What is Redundancy? | What is a Single Point of Failure? | What is Concentration Risk? | What are Data Centres? | What is HVAC?