Elasticsearch
What it is: Distributed search and analytics engine built on Apache Lucene. Real-time full-text search, log analysis, metrics.
What It Does Best
Full-text search. Relevance scoring, fuzzy matching, autocomplete. Search UIs that actually work.
Log analytics. ELK Stack (Elasticsearch, Logstash, Kibana). Ingest, search, visualize logs at scale.
Real-time indexing. Documents searchable within seconds. No batch processing delays.
Pricing
Free core. Open source, SSPL/Elastic License. Elastic Cloud (managed): ~$95/mo starter, scales with usage.
When to Use It
✅ Application search functionality
✅ Log and event data analysis
✅ Real-time analytics dashboards
✅ E-commerce product search
When NOT to Use It
❌ Primary transactional database (not ACID compliant)
❌ Relational data with complex joins
❌ Guaranteed data durability (use proper backups)
Bottom line: The search engine for everything. Application search, log analytics, security monitoring. Powerful query DSL, but complex to tune. Worth the learning curve for search-heavy workloads.