Mission-Critical Systems
When to Use
- Classify criticality tiers (mission-critical, business-critical, important) with explicit impact criteria
- Set availability, integrity, and continuity objectives (uptime, RTO/RPO, MTPD, data loss tolerance)
- Map dependencies, failure domains, and blast radius for severe-impact services
- Select architecture patterns—active-active, geo-redundancy, quorum, deterministic execution, fail-safe defaults
- Define change and release governance—hold points, CAB tiers, emergency change, rollback criteria
- Tailor monitoring, alerting, and escalation to criticality (SLOs alone are insufficient for Tier 0)
- Align engineering with contractual SLAs, sector regulation, and continuity obligations (generic framing)
- Produce criticality registers, architecture decision records, and governance briefs for leadership
When NOT to Use
- Own SLI/SLO definitions, error-budget policy, burn-rate alerting, and toil reduction →
site-reliability-engineer
- Establish failure-prevention culture, HRO principles, stop-the-line, and defect-escape metrics →
zero-tolerance-for-failure
- Run live incident war room, containment, and forensic preservation →
incident-responder
- Design backup/immutability, ransomware recovery, and resilience test evidence →
cyber-resilience-engineer
- Own enterprise BCM program, BIA facilitation, and regulatory BCM policy →
bcm-disaster-recovery-specialist
- Enterprise security reference architecture and control frameworks without tiering lens →
enterprise-security-architect
- Greenfield integration patterns and ADRs without criticality classification →
senior-system-architecture
- Cleared program ATO, inspection, and personnel security without operational tiering →
classified-cyber-security-senior-manager
- CI compile/lint gates without release governance for critical services →
build-validator
Related skills
| Need |
Skill |
| SLOs, error budgets, reliability dashboards, capacity toil |
site-reliability-engineer |
| HRO mindset, verification gates, fail-safe design, pre-mortem/FMEA |
zero-tolerance-for-failure |
| RTO/RPO recovery architecture, immutability, attack playbooks |
cyber-resilience-engineer |
| Enterprise BCM/DR program, tabletops, crisis comms |
bcm-disaster-recovery-specialist |
| Active CSIRT response and containment |
incident-responder |
| Incident program, SEV, on-call, postmortem process |
incident-management-engineer |
| NFRs, architecture review, ADRs |
senior-system-architecture |
| Security reference architecture, zero trust, governance |
enterprise-security-architect |
| Cleared program governance and accreditation interfaces |
classified-cyber-security-senior-manager |
| Cloud DR regions, landing zone, service placement |
cloud-engineer |
Core Workflows
1. Scope and criticality tiering
Define what “mission-critical” means in context; classify services and data; document drivers.
See references/mission_critical_scope_and_tiering.md.
2. Objectives: availability, integrity, continuity
Set measurable targets and exclusions; align tiers to RTO/RPO/MTPD and integrity classes.
See references/objectives_availability_integrity_continuity.md.
3. Architecture patterns for critical systems
Choose redundancy, partitioning, determinism, and degradation modes for Tier 0/1 workloads.
See references/architecture_patterns_for_critical_systems.md.
4. Dependencies and blast radius
Map upstream/downstream, shared fate, control planes, and containment boundaries.
See references/dependencies_and_blast_radius.md.
5. Change control and release governance
Tier releases, evidence gates, emergency change, and rollback for high-criticality paths.
See references/change_control_and_release_governance.md.
6. Operations, monitoring, and escalation
Observability depth, synthetic probes, runbooks, and escalation matched to impact.
See references/operations_monitoring_and_escalation.md.
Outputs
- Criticality register — tier, owner, impact narrative, objectives, last review
- Objectives sheet — availability, integrity, RTO/RPO/MTPD per tier with measurement method
- Dependency / blast-radius map — failure domains, shared components, isolation notes
- Architecture decision pack — pattern choice, trade-offs, degradation and fail-safe behavior
- Release governance matrix — change type × tier → gates, approvers, evidence, rollback
- Operations brief — alert routes, escalation tree, runbook index, drill calendar hooks
Principles
- Tier before tooling — criticality drives architecture and governance; do not retrofit labels after build
- Integrity equals availability — corruption or unauthorized change can be worse than downtime
- Contain blast radius — shared control planes and “single throat to choke” are Tier 0 risks
- Govern change proportionally — higher tier → more evidence, independence, and rollback discipline
- Measure what customers and regulators care about — pair SRE SLIs with tier-specific continuity proofs
- Pair with peers — reliability math (SRE), prevention culture (zero-tolerance), recovery (resilience), incidents (IR)
1---2name: mission-critical3description: Guides mission-critical system framing—tiering (mission-critical vs business-critical vs important), availability/integrity/continuity objectives, dependency and blast-radius mapping, architecture patterns (active-active, geo-redundancy, deterministic behavior), change/release governance, monitoring and escalation by criticality, and generic regulatory/contractual drivers (finance, healthcare, public safety, defense industrial base). Use when classifying criticality, setting RTO/RPO/MTPD and integrity targets, designing redundant architectures, mapping failure domains, governing Tier 0/1 releases, or ops escalation—not SRE error budgets only (site-reliability-engineer), HRO/prevention culture only (zero-tolerance-for-failure), incident command (incident-responder), recovery engineering only (cyber-resilience-engineer), enterprise security architecture only (enterprise-security-architect), ADRs without tiering (senior-system-architecture), or classified ATO only (classified-cyber-security-senior-manager).4---56# Mission-Critical Systems78## When to Use910- Classify **criticality tiers** (mission-critical, business-critical, important) with explicit impact criteria11- Set **availability, integrity, and continuity** objectives (uptime, RTO/RPO, MTPD, data loss tolerance)12- Map **dependencies**, failure domains, and **blast radius** for severe-impact services13- Select **architecture patterns**—active-active, geo-redundancy, quorum, deterministic execution, fail-safe defaults14- Define **change and release governance**—hold points, CAB tiers, emergency change, rollback criteria15- Tailor **monitoring, alerting, and escalation** to criticality (SLOs alone are insufficient for Tier 0)16- Align engineering with **contractual SLAs**, sector regulation, and continuity obligations (generic framing)17- Produce **criticality registers**, architecture decision records, and governance briefs for leadership1819## When NOT to Use2021- Own SLI/SLO definitions, error-budget policy, burn-rate alerting, and toil reduction → `site-reliability-engineer`22- Establish failure-prevention culture, HRO principles, stop-the-line, and defect-escape metrics → `zero-tolerance-for-failure`23- Run live incident war room, containment, and forensic preservation → `incident-responder`24- Design backup/immutability, ransomware recovery, and resilience test evidence → `cyber-resilience-engineer`25- Own enterprise BCM program, BIA facilitation, and regulatory BCM policy → `bcm-disaster-recovery-specialist`26- Enterprise security reference architecture and control frameworks without tiering lens → `enterprise-security-architect`27- Greenfield integration patterns and ADRs without criticality classification → `senior-system-architecture`28- Cleared program ATO, inspection, and personnel security without operational tiering → `classified-cyber-security-senior-manager`29- CI compile/lint gates without release governance for critical services → `build-validator`3031## Related skills3233| Need | Skill |34|---|---|35| SLOs, error budgets, reliability dashboards, capacity toil | `site-reliability-engineer` |36| HRO mindset, verification gates, fail-safe design, pre-mortem/FMEA | `zero-tolerance-for-failure` |37| RTO/RPO recovery architecture, immutability, attack playbooks | `cyber-resilience-engineer` |38| Enterprise BCM/DR program, tabletops, crisis comms | `bcm-disaster-recovery-specialist` |39| Active CSIRT response and containment | `incident-responder` |40| Incident program, SEV, on-call, postmortem process | `incident-management-engineer` |41| NFRs, architecture review, ADRs | `senior-system-architecture` |42| Security reference architecture, zero trust, governance | `enterprise-security-architect` |43| Cleared program governance and accreditation interfaces | `classified-cyber-security-senior-manager` |44| Cloud DR regions, landing zone, service placement | `cloud-engineer` |4546## Core Workflows4748### 1. Scope and criticality tiering4950Define what “mission-critical” means in context; classify services and data; document drivers.5152**See `references/mission_critical_scope_and_tiering.md`.**5354### 2. Objectives: availability, integrity, continuity5556Set measurable targets and exclusions; align tiers to RTO/RPO/MTPD and integrity classes.5758**See `references/objectives_availability_integrity_continuity.md`.**5960### 3. Architecture patterns for critical systems6162Choose redundancy, partitioning, determinism, and degradation modes for Tier 0/1 workloads.6364**See `references/architecture_patterns_for_critical_systems.md`.**6566### 4. Dependencies and blast radius6768Map upstream/downstream, shared fate, control planes, and containment boundaries.6970**See `references/dependencies_and_blast_radius.md`.**7172### 5. Change control and release governance7374Tier releases, evidence gates, emergency change, and rollback for high-criticality paths.7576**See `references/change_control_and_release_governance.md`.**7778### 6. Operations, monitoring, and escalation7980Observability depth, synthetic probes, runbooks, and escalation matched to impact.8182**See `references/operations_monitoring_and_escalation.md`.**8384## Outputs8586- **Criticality register** — tier, owner, impact narrative, objectives, last review87- **Objectives sheet** — availability, integrity, RTO/RPO/MTPD per tier with measurement method88- **Dependency / blast-radius map** — failure domains, shared components, isolation notes89- **Architecture decision pack** — pattern choice, trade-offs, degradation and fail-safe behavior90- **Release governance matrix** — change type × tier → gates, approvers, evidence, rollback91- **Operations brief** — alert routes, escalation tree, runbook index, drill calendar hooks9293## Principles9495- **Tier before tooling** — criticality drives architecture and governance; do not retrofit labels after build96- **Integrity equals availability** — corruption or unauthorized change can be worse than downtime97- **Contain blast radius** — shared control planes and “single throat to choke” are Tier 0 risks98- **Govern change proportionally** — higher tier → more evidence, independence, and rollback discipline99- **Measure what customers and regulators care about** — pair SRE SLIs with tier-specific continuity proofs100- **Pair with peers** — reliability math (SRE), prevention culture (zero-tolerance), recovery (resilience), incidents (IR)
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