Reserved Instance Flexibility

I. Formal Definition

The capability of a reservation to apply across multiple instance families, sizes, or operating systems through provider-specific flexibility features such as size flexibility, regional scope, and instance family flexibility. RI flexibility reduces the planning risk of reservations by absorbing fleet evolution. The federation requires reservation purchases to default to the most flexible compatible posture unless a documented reason justifies a more restrictive commitment under UFMS-001:2.4(d). Flexibility decisions are reviewed at the annual procurement consolidation.

II. Etymology

A coinage of cloud provider literature in the mid 2010s; the term spread as RI products evolved to absorb the operational pain of strict reservation matching.

III. Federation Usage

Federation members default to maximally flexible reservations. Restrictive reservations are documented with rationale. Flexibility utilisation is reviewed at the annual procurement consolidation and reported in the procurement register under MEV-Annex:3.2.

IV. Related Terms

• ri-utilization
• reserved-instance
• instance-family
• commitment-utilization

V. Authoritative Citations

• UFMS-001:2.4UFMS Article II - RI Flexibility
• MEV-Annex:3.2MEV Annex III - Flexibility Reporting

VI. Citation in BibTeX

@misc{ifo4_glossary_ri_flexibility,
  title        = {{Reserved Instance Flexibility}},
  author       = {{IFO4 Federation Editorial Board}},
  howpublished = {{IFO4 Federation Glossary, slug \texttt{ri-flexibility}}},
  year         = {2026},
  url          = {https://ifo4.org/glossary/ri-flexibility},
  note         = {Category: FinOps; key: ReservedInstanceFlexibility}
}

VII. Challenge This Definition

Federation members and accredited practitioners may challenge any entry under TGS-002:1.7. Filed challenges are routed to the editorial board, triaged into the revision register, and resolved in writing on the public docket. The slug remains stable through any revision.