How OpenSearch Works — Architecture, Internals & Real-Time Search Explained

In the era of big data, fast and flexible search is a necessity — whether you're analyzing logs, powering an e-commerce search bar, or visualizing metrics in real time. That’s where OpenSearch shines.

OpenSearch is a powerful, open-source search and analytics engine — a fork of Elasticsearch maintained by Amazon and the open-source community. It provides full-text search, distributed indexing, real-time analytics, and slick dashboards — all built for scalability and openness.

So how does it actually work?

Let’s dive in.

🚀 What Is OpenSearch?

OpenSearch is an open-source alternative to Elasticsearch, licensed under Apache 2.0. It was created after Elasticsearch switched to a non-open-source license, and it's backed by a growing ecosystem of contributors and users.

Key Features:

🔎 Full-text search and filtering
📈 Real-time metrics and analytics
🛡️ Built-in security and access control
📊 OpenSearch Dashboards (Kibana fork)
⚙️ Plugin support for alerting, anomaly detection, and more

🧠 How OpenSearch Works — Step by Step

1. Ingest Data

Your data comes from logs, apps, metrics pipelines, or shippers like Beats, Logstash, or Fluentd. You can also send data directly via the REST API.

2. Index Data

OpenSearch transforms each document into an inverted index (just like a book index), optimized for fast searching. During this phase:

Fields are tokenized and analyzed
Documents are split into shards
Replicas are created for redundancy

3. Distribute & Store

OpenSearch distributes shards across data nodes in the cluster. This makes it horizontally scalable — you can store and search terabytes of data by just adding more nodes.

4. Search & Query

Users or applications can send queries (via the API or dashboard). OpenSearch:

Routes the query through a coordinating node
Broadcasts the query to relevant shards
Gathers and ranks results using the BM25 algorithm
Returns the result in real time

5. Analyze & Visualize

Use OpenSearch Dashboards to explore your data with:

Charts, maps, and tables
Filters and saved searches
Alerts and anomaly detection

🧩 OpenSearch Architecture Diagram

Here’s a high-level diagram that shows how the software modules connect:

graph TD
    UI["OpenSearch Dashboards<br/>(Web UI)"] --> API["REST API"]
    Ingest["Data Ingest Tools<br/>(Beats, Logstash, Fluentd)"] --> API
    App["Custom Applications<br/>(Microservices, Backends)"] --> API

    API --> Coord["Coordinating Node"]
    Coord -->|Writes| IngestNode["Ingest Node<br/>(Optional Preprocessing)"]
    Coord -->|Search/Query| QueryEngine["Query Engine"]

    IngestNode --> Indexer["Indexing Engine"]
    Indexer --> Shards["Shards<br/>(Distributed on Data Nodes)"]

    QueryEngine --> Shards
    Shards --> QueryEngine
    QueryEngine --> Coord
    Coord --> API

    Security["Security Module<br/>(RBAC, TLS, Audit Logs)"] --> API

    Dashboards["Visual Plugins<br/>(Charts, Maps, Alerts)"] --> UI

🔐 Security & Extensibility

OpenSearch includes robust, enterprise-ready security:

Role-based access control (RBAC)
TLS encryption for data in transit
Audit logging
API key management

You can also enable modules like:

⚠️ Alerting: Define triggers and notifications.
🤖 Anomaly Detection: Detect unusual patterns using machine learning.
🧩 Custom Plugins: Build and extend functionality easily.

✅ Why Choose OpenSearch?

💸 Free and Open under Apache 2.0
⚖️ Scales Horizontally with large datasets
🧠 Built-in analytics, visualizations, and monitoring
🔐 Secure by default for enterprise use
🔌 Flexible integration with modern DevOps stacks

🏁 Final Thoughts

OpenSearch is more than just a search engine — it’s a real-time, scalable analytics platform. Whether you’re building search into an app, managing logs, or monitoring infrastructure, understanding its architecture helps you unlock its full power.