Catalog
concept#Architecture#Integration#Observability#Reliability

Client State

Concept for managing state on the client side, including session, UI and cached data. Describes design aspects, synchronization and consistency requirements.

Client state denotes information held on the client side of a distributed system to represent user session, UI state or cached data.
Established
Medium

Classification

  • Medium
  • Technical
  • Architectural
  • Intermediate

Technical context

Backend API with conflict resolution endpointsClient persistence layer (IndexedDB, localStorage)Service worker for offline caching and background sync

Principles & goals

Minimize sensitive data in local storage.Clearly separate transient UI state and persistable data.Define deterministic synchronization and conflict resolution strategies.
Build
Domain, Team

Use cases & scenarios

Compromises

  • Inconsistencies with concurrent edits without conflict policy.
  • Data loss due to outdated migration strategies.
  • Attack vectors via local storage of sensitive tokens.
  • Persist only necessary data and anonymize sensitive information.
  • Use versioned updates and deterministic merges for conflicts.
  • Monitor cache hits, synchronization latencies and conflict rates.

I/O & resources

  • Definition of state to persist and granularity.
  • Synchronization and conflict resolution policies.
  • Security requirements and encryption policies.
  • Local persistence of relevant state fragments.
  • Synchronization protocols and reconciliation logs.
  • Metrics on cache performance and synchronization behavior.

Description

Client state denotes information held on the client side of a distributed system to represent user session, UI state or cached data. It reduces server load and supports offline experiences but requires synchronization, consistency strategies and security considerations. Appropriate patterns balance latency, complexity and reliability.

✔

  • Faster response times via local access.
  • Enables offline capability and resilient UX.
  • Reduces load and latency on server infrastructure.

✖

  • Increased implementation effort for consistency and synchronization.
  • Limited storage and varying browser/platform APIs.
  • Risk of security issues if stored improperly.

  • Cache hit rate

    Share of requests served from local client cache.

  • Synchronization latency

    Time between local change and successful server synchronization.

  • Incidence of conflicts

    Frequency of conflicts occurring during synchronization.

Progressive Web App using IndexedDB caching

Offline-capable PWA stores form data and articles in IndexedDB and synchronizes when online.

SPA with central state container

React app uses a central store for UI state and persists relevant parts between sessions.

Mobile app with CRDTs

Mobile collaboration app uses CRDTs for local edits and automatic merge on synchronization.

1

Identify which parts of the state should be held locally and why.

2

Choose suitable persistence APIs and define storage schemas.

3

Develop synchronization rules, versioning and conflict policy.

4

Implement security measures, tests and metric collection.

⚠️ Technical debt & bottlenecks

  • Ad-hoc persistence implemented without versioning.
  • Lack of observability for reconciliation processes.
  • Insufficient security review of sensitive local data.
Browser storage limitsNetwork synchronization windowsConflict resolution complexity
  • Persisting full database copies in the browser for performance.
  • Relying on local data as sole source after extended offline period.
  • Implementing ad-hoc conflict solutions without tests.
  • Underestimating platform-specific storage limits.
  • Missing migration paths for schema changes.
  • Untested synchronization edge cases leading to data loss.
Knowledge of distributed systems and consistency modelsExperience with client storage APIs and securityAbility to design synchronization and conflict-resolution algorithms
User workflow latency requirementsExpected offline/low-connectivity usageSecurity and privacy requirements
  • • Browser and platform inconsistencies in storage APIs.
  • • Regulatory requirements for handling personal data.
  • • Limited persistent storage availability on mobile devices.