Elasticsearch

Read-Heavy Application

A CMS for publishing and serving structured content: articles, documentation, product pages, and localized variants: where read APIs serve 50–100x more traffic than editorial write APIs. PostgreSQL stores the content graph (articles, authors, categories, taxonomy) and workflow state (draft, in-review, scheduled, published). Redis caches published content objects for read APIs. Elasticsearch powers full-text content search with faceting and relevance ranking. Cache invalidation on publish must be fast and complete; N+1 query patterns on content relationship traversal are the dominant database performance risk during reads.

Multi-Tenant SaaS

A multi-tenant developer tooling platform providing CI/CD pipeline execution, log aggregation, code analysis, and dependency scanning across isolated tenant organizations. Tenant isolation is the primary correctness constraint: a security boundary violation between tenants is a critical incident, not a performance event. PostgreSQL row-level security enforces data isolation; Redis manages job queues and distributed locks; Elasticsearch indexes pipeline log output for search; Kafka delivers webhook events to tenant-registered endpoints; MinIO stores pipeline artifacts. Resource quota enforcement prevents any single tenant's burst from affecting others.

Marketplace Platform

An e-commerce order lifecycle platform handling cart, checkout, payment, fulfillment, and returns across a mixed read/write workload where product discovery is read-heavy, checkout is write-transactional, and fulfillment is event-driven. The saga pattern orchestrates multi-step checkout: reserve inventory → charge payment → confirm order → notify fulfillment. PostgreSQL owns order records and inventory with row-level locking; Redis holds session state and cart contents with sub-millisecond access; RabbitMQ delivers fulfillment notifications with dead-letter handling; Elasticsearch serves product search and order history with faceted navigation. CQRS separates the write command path from the read model: the order read model is denormalized for fast order history queries without joining across domain tables.

Analytics Pipeline

A metrics, logs, and traces ingestion and query platform built to absorb the telemetry output of a production system fleet: including the telemetry volume spikes that accompany the incidents the platform is meant to detect. ClickHouse stores metrics data with automatic time-based rollup via continuous materialized views; TimescaleDB provides complementary time-series storage for high-cardinality alert evaluation; Kafka buffers the ingestion stream against downstream write pressure, decoupling ingest acceptance rate from storage write throughput; Elasticsearch serves log full-text search and structured field filtering; Redis caches dashboard query results and active alert state for sub-100ms alert evaluation latency. The alert engine evaluates threshold and anomaly rules against pre-computed materialized views, not raw data, to bound alert evaluation cost independent of ingestion volume.

Search-Heavy Application

A content platform architecture centered on Elasticsearch for full-text search, faceted navigation, and ranked results, with PostgreSQL as the transactional source of truth and Redis for session management and hot content caching. WAL-based CDC maintains index freshness by streaming PostgreSQL changes into Elasticsearch asynchronously. The core tension is between search index freshness, query performance, and index maintenance cost under high write volume.

Marketplace Platform

A two-sided marketplace architecture serving buyers, sellers, listings, transactions, search, and notifications from a shared infrastructure, where multiple independent domains must coordinate without tight coupling. Event sourcing captures every state transition; the saga pattern orchestrates multi-step transactions (create order, reserve inventory, charge payment, notify seller) with compensating transactions for partial failures. Kafka decouples domain event publication from consumption; RabbitMQ handles notification fanout; Elasticsearch serves listing search; Redis caches listing display and session state.