Fix #741: Implement Distributed Multi-Tier Cache & Atomic Invalidation

[SatyamPandey-07]

closes #741

Key Features Implemented:
L1/L2 Tiered Storage: Created

utils/multiTierCache.js
providing sub-millisecond local L1 (in-memory) retrieval with fallback to a simulated L2 (distributed) store. This ensures data is cached close to the application logic.
Cascading Invalidation Engine: Developed

services/invalidationManager.js
to manage dependency-aware cache purges. It handles complex entity relationships (e.g., Workspace → Analytics → Reports) with recursive cycle detection.
Epoch-Based Versioning: Enhanced

models/Workspace.js
with a cacheEpoch field. Every cache key is versioned by this epoch, allowing for "Atomic Invalidation" of all cached data for a workspace with a single integer increment.
Versioned Cache Middleware: Implemented

middleware/cacheSync.js
which automatically resolves the current workspace epoch and injects key-generation helpers into every request context.
Analytics & Report Overhaul:
Refactored

services/analyticsService.js
to use tiered caching for Z-Score anomalies, volatility analysis, and spending trends.
Enhanced

services/reportService.js
to persist complex financial report results (Income Statements, P&L) in the tiered cache, reducing re-computation time.
Automated Maintenance: Created

jobs/cachePruner.js
to periodically sweep the L1 memory tier and simulated L2 store, ensuring expired entries are purged to maintain a lean memory footprint.
Technical Specification: Authored

CACHE_ARCHITECTURE.md
, providing a deep dive into the tiered strategy, epoch versioning logic, and invalidation workflows.
Consistency Test Suite: Developed

tests/cacheConsistency.test.js
which validates L1/L2 fallback logic, expiration handling, and multi-step cascading purges through the invalidation manager.

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🎉 Thanks for the PR, @SatyamPandey-07!

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Project	Deployment	Actions	Updated (UTC)
expenseflow	Ready	Preview, Comment	Feb 23, 2026 4:37am