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Designing scalable systems for the AI era

24 Jun 2026 · 5 min read

For much of the cloud era, scalability was discussed primarily as a capacity problem. Could the database sustain more transactions? Could another application instance be added automatically? Could traffic fail over between regions? Could the architecture support ten times the number of users without a corresponding increase in cost?

Those questions remain important. AI adds a different dimension.

Modern systems increasingly contain probabilistic components, external model dependencies and software capable of selecting or initiating actions rather than merely processing predetermined instructions. At the same time, AI is being introduced into banking, government, healthcare, telecommunications, manufacturing, utilities and national infrastructure — environments in which availability is only one part of system quality.

A system that scales while losing control is not well architected.

For the AI era, scalability increasingly means increasing capability without allowing operational risk, dependency and blast radius to grow at the same rate.

Probabilistic reasoning needs deterministic boundaries

The first architectural distinction is between reasoning and authority.

A language model may be excellent at interpreting an incident report, correlating evidence or recommending the next action. It is still a probabilistic component whose output can change with context, model version and orchestration. The fact that the recommendation is usually correct does not mean the model should become the system of record for whether an action is authorised.

An agent can determine that a production service appears to require a restart. A deterministic control can still verify whether the requesting identity has authority, whether the target is inside the permitted scope, whether the change window is open and whether a secondary approval is required. An AI system can identify a suspicious banking transaction while an independent policy engine remains responsible for deciding whether an account may actually be frozen.

This separation becomes even more important as AI evolves from recommendation into execution.

A prompt is not an access-control mechanism, just as natural-language reasoning is not a substitute for transaction integrity. The architecture should assume that model reasoning can be wrong and ensure that authority boundaries remain valid when it is.

Design the degraded service before the ideal service

Highly available architectures are often designed around total failure: a server stops responding, a region disappears, traffic moves elsewhere.

Real incidents are frequently partial.

A model endpoint remains available but latency increases beyond the operational threshold. The identity service can validate existing sessions but cannot establish new entitlements. One external data source becomes stale. Connectivity to a cloud region is unstable rather than completely unavailable. A new model version returns valid responses but behaves differently in edge cases.

Resilience therefore requires explicit service modes.

An AI-dependent process should know what remains possible when inference is unavailable. A critical workflow may fall back to deterministic rules, reduced automation or human operation. A service may continue in read-only mode. Actions can be queued if they are safe to execute later, while other actions should be rejected immediately if their current authority cannot be established.

The point is not to create a fallback for every imaginable failure. It is to identify the functions that are essential and design the minimum safe operating mode in advance.

ISO 22301 provides a structured management framework for business continuity and recovery from disruption. In EU environments where NIS2 applies, business continuity, backup, disaster recovery and crisis management also form part of the Directive’s cybersecurity risk-management expectations.

For entities covered by the Critical Entities Resilience framework, this logic extends beyond cyber availability into broader organisational resilience. Recent EU guidance explicitly links continuity planning to business-impact analysis, recovery priorities, RTO/RPO and tested recovery arrangements.

Recovery needs to restore meaning, not only infrastructure

Recovery Time Objective and Recovery Point Objective remain valuable measures, but AI systems introduce failure states that they do not capture well.

A vector database can be restored within its RTO while lacking the latest permission changes. A model service can return to healthy status while a new version materially changes tool-selection behaviour. An agentic workflow can restart from persisted state even though an external transaction was already committed before the failure occurred.

The infrastructure has recovered. The business state may not have.

This introduces a requirement for semantic and workflow recovery. The system needs to determine whether knowledge is still authoritative, whether interrupted actions can resume idempotently, whether side effects need reconciliation and whether a changed AI component must pass evaluation before it regains production authority.

For high-consequence systems, availability without state integrity can be more dangerous than downtime because the service appears healthy while making decisions against an invalid state.

Multi-region does not remove correlated failure

Two cloud regions can share more dependencies than an architecture diagram suggests.

They may rely on the same identity provider, DNS infrastructure, control plane, software supply chain, CI/CD credentials, telecommunications provider, model service or encryption-key hierarchy. A compromise or outage in one of those common services can therefore defeat the geographic redundancy.

Resilience analysis should map correlated dependencies rather than counting regions.

For government and sovereign workloads, the same analysis needs to include jurisdiction and administrative control. It matters where the service runs, but it also matters who can administer it, who controls encryption keys, where telemetry and backups are processed, which control plane can change infrastructure and what happens to those boundaries during disaster recovery.

A workload is not sovereign simply because its primary database is stored inside a national border.

Sovereignty is an end-to-end property of operational control.

AI at the IT/OT boundary requires a different safety model

Industrial and operational-technology environments make these architectural distinctions especially important.

In enterprise IT, an incorrect software action may interrupt a business process. In an industrial system it can influence physical production, equipment, availability or safety. This changes the acceptable relationship between probabilistic AI and control authority.

IEC 62443 provides the core international cybersecurity framework for industrial automation and control systems. At system level, IEC 62443-3-3 defines technical requirements and security levels around foundational areas including identification and authentication, use control, system integrity, restricted data flow, timely response and resource availability. Its system model uses zones and conduits to structure trust and communication boundaries.

For an AI-enabled industrial architecture, this generally argues against allowing a model to collapse analytical and operational authority into the same trust boundary. AI can interpret telemetry, detect anomalies, support operators or prepare actions while deterministic controls, segmentation and safety mechanisms continue to govern what can actually occur in the process environment.

Higher model accuracy does not remove the need for those boundaries.

Financial systems have a distinct resilience obligation

Banking and financial services add another architecture layer through DORA.

DORA requires in-scope financial entities to maintain a documented ICT risk-management framework, protect availability, authenticity, integrity and confidentiality, understand key third-party dependencies and preserve the continuity of critical or important functions through appropriate response and recovery measures.

That changes the evaluation of AI infrastructure.

A model provider supporting a critical financial function should not be assessed solely on quality, latency and price. The architecture also needs to consider concentration risk, provider outage, substitution, data handling, incident visibility, contractual dependencies and the organisation’s ability to continue the business function if that external capability disappears.

This can lead to a technically less elegant architecture that is operationally stronger because it gives the regulated entity more control over recovery and exit.

That is not compliance compromising architecture. It is architecture correctly incorporating the actual operating environment.

Product architecture now includes vulnerability lifecycle

There is a separate consideration when the system is a product with digital elements placed on the EU market rather than purely an internal platform.

The Cyber Resilience Act establishes cybersecurity requirements for covered products throughout design, development and vulnerability handling. Importantly for modern software, its scope can include remote data processing where that processing is necessary for the product to perform one of its functions.

That matters for cloud-connected and AI-enabled products because the functional product can span local software, APIs and remote processing.

Security support periods, vulnerability handling, security updates, component dependencies and secure decommissioning therefore become architectural lifecycle concerns. The supplier cannot treat cybersecurity as complete when version 1.0 is released.

For industrial products, IEC 62443-4-1 adds a sector-specific secure development lifecycle covering areas such as security requirements, secure design and implementation, verification, defect management, patch management and product end-of-life.

Again, the standard should be used where the sector and product justify it, not applied indiscriminately to every enterprise application.

Regulation should follow the workload

NIS2, CER, DORA, the Cyber Resilience Act, IEC 62443 and ISO 22301 solve different problems and apply to different scopes. Treating them as one generic compliance bundle is a sign that the architecture has not been classified properly.

The correct sequence is the opposite.

First determine the service, intended use, sector, jurisdiction and consequence of failure. Then establish which legal, regulatory and standards frameworks materially affect it. Only then should those requirements be translated into technical properties such as segmentation, identity architecture, supplier controls, recovery, auditability, vulnerability handling and sovereign operation.

When that work happens before platform and provider selection, regulation improves the design.

When it happens at the end, it becomes expensive remediation.

Scale should increase capability without increasing uncertainty

A mature AI-era architecture can grow in users, data, regions, models and automation while keeping its authority boundaries visible.

It can replace a model without rebuilding the business process around it. It understands which dependencies can fail together. It knows which functions remain available when AI is not. It preserves operational control across regions and suppliers. It can prove what happened after an incident rather than reconstructing it from partial logs.

That is a stronger definition of scalability than transactions per second.

The architecture has scaled when capability increases without an uncontrolled increase in dependency, blast radius and operational risk.

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