When you're building a data-backed application, one of the first decisions you face is choosing the right database architecture. The distinction between OLTP (Online Transaction Processing) and OLAP (Online Analytical Processing) databases determines whether your system can handle real-time transactions, complex analytics, or both.
This article explains what OLTP and OLAP databases do, how they differ, when to use each type, and how modern architectures combine them to serve both operational and analytical workloads.
What is an OLTP database
OLTP stands for Online Transaction Processing. These databases handle real-time transactions like processing a credit card payment, updating inventory after a sale, or booking a hotel room.
Online transaction processing definition
An OLTP database processes individual transactions as they happen, one at a time or thousands at once. Each transaction either completes fully or doesn't happen at all, which prevents problems like charging a customer twice or overselling inventory. This guarantee comes from ACID properties (Atomicity, Consistency, Isolation, Durability), which keep data accurate even when many users modify records simultaneously.
Common OLTP workload patterns
OLTP systems handle three main types of operations:
- Point lookups: Fetching a single record by its ID, like retrieving a user's account details
- Small updates: Changing one or a few records, like marking an order as shipped
- Individual inserts: Adding new records as events occur, like recording a new customer signup
Each operation touches only a small amount of data, usually just one row or a handful of related rows. Response times typically measure in milliseconds because users expect instant feedback when they click a button or submit a form.
Popular OLTP systems
PostgreSQL and MySQL dominate the open-source OLTP space, though they face challenges with analytical workloads, while Oracle Database and Microsoft SQL Server lead in enterprise environments. These databases store data in rows, keeping all columns for a single record together on disk. This row-oriented storage makes it fast to read or write complete records, which is exactly what transactional applications do most often. For a detailed comparison of how PostgreSQL compares to columnar databases like ClickHouse for analytical workloads, see our ClickHouse vs PostgreSQL comparison. Similarly, see how ClickHouse compares to MySQL for analytics, and for AWS users, our Aurora MySQL vs ClickHouse performance comparison.
What is an OLAP database
OLAP stands for Online Analytical Processing. These databases answer questions about your data by scanning and aggregating large volumes of historical records.
Online analytical processing definition
An OLAP database analyzes historical data to find patterns, calculate trends, and generate reports. Instead of processing individual transactions, it reads millions or billions of rows to answer questions like "What were our best-selling products last quarter?" or "How many users signed up each week over the past year?" The queries take longer than OLTP operations, often seconds or minutes, but they provide insights that help with business decisions.
Typical OLAP query patterns
OLAP queries look different from transactional queries:
- Aggregations: Computing SUM, COUNT, AVG, or MAX across huge datasets
- Multi-dimensional grouping: Analyzing data by product, region, and time period simultaneously
- Time-series analysis: Examining how metrics change over weeks, months, or years
A single analytical query might scan terabytes of data, reading millions of rows per second. This would overwhelm an OLTP database, but OLAP systems handle it efficiently through specialized storage and processing techniques.
Widely used OLAP platforms
ClickHouse, Snowflake, Google BigQuery, and Amazon Redshift lead the OLAP market. These platforms store data in columns rather than rows, keeping all values for a single field together on disk. When a query only needs a few columns from a table with hundreds of fields, the database can skip reading the irrelevant columns entirely, making queries much faster. For AI and ML workloads, cloud-native alternatives like Databend offer elastic scaling by separating storage and compute.
OLTP vs OLAP key differences
The choice between OLTP and OLAP comes down to understanding what each system optimizes for.
Purpose and workload
OLTP databases handle operational work: creating orders, updating account balances, deleting old records. Every operation either succeeds completely or fails without leaving partial changes. OLAP databases handle analytical work: scanning large datasets, computing aggregates, generating reports. The focus shifts from individual transactions to bulk operations that process millions of rows at once.
Data model and storage
OLTP databases use normalized schemas that split data across multiple related tables. A customer order might span five tables: customers, orders, order_items, products, and shipping_addresses. This normalization prevents duplicate data and makes updates efficient, though it means most queries join several tables together.
OLAP databases denormalize data into wider tables that combine related information. A sales fact table might include customer name, product category, and order details in the same row. This reduces the number of joins needed for analytical queries, trading some storage efficiency for query performance.
Query latency and concurrency
OLTP systems deliver millisecond response times for thousands of concurrent small operations. Each query touches just a few rows, maybe fetching a single user record or updating an order status. OLAP systems handle fewer concurrent queries, but each one scans millions of rows and takes seconds to minutes. The database processes these heavy queries in parallel across multiple CPU cores or cluster nodes.
Ingestion and ETL flow
OLTP databases receive data directly from applications as transactions occur. When a user clicks "checkout," the application writes to the OLTP database immediately. OLAP databases typically load data from OLTP systems through ETL (Extract, Transform, Load) or ELT (Extract, Load, Transform) pipelines. Change data capture (CDC) tools track modifications in OLTP databases and replicate them to OLAP systems, often with just seconds of delay.
Cost and scale trade-offs
OLTP systems often scale vertically with expensive high-end hardware to maintain sub-millisecond response times. A single powerful server with fast SSDs and lots of RAM can handle millions of transactions per day. OLAP systems scale horizontally across clusters of commodity servers, distributing data and query processing to achieve high throughput at lower cost per gigabyte stored.
When to use an OLTP database
Pick OLTP when your application processes individual transactions that need immediate consistency and fast response times.
High-volume transactions
E-commerce checkouts, banking transfers, and reservation systems generate thousands of small transactions per second. Each transaction modifies just a few records but requires immediate confirmation. An OLTP database processes these operations quickly while preventing conflicts like double-booking a flight seat or overselling inventory.
Strict consistency requirements
Financial systems and inventory management can't tolerate even temporary inconsistencies. OLTP databases provide ACID guarantees through locking and isolation mechanisms that coordinate concurrent access. When two users try to book the last hotel room simultaneously, the database ensures only one succeeds.
Low-latency point lookups
User authentication, product catalog searches, and account balance checks demand instant responses. OLTP databases optimize for retrieving single records by primary key using B-tree indexes, typically returning results in under a millisecond. This makes them ideal for interactive applications where users expect immediate feedback.
When to use an OLAP database
Choose OLAP when you need to analyze historical data through complex queries that aggregate millions of rows.
Complex aggregations at scale
Revenue reports across regions, customer segmentation analysis, and performance dashboards all require scanning large datasets to compute aggregates. OLAP databases use columnar storage and parallel processing to make these queries fast. What might take minutes in an OLTP database often completes in seconds with OLAP.
Historical trend analysis
Year-over-year comparisons, seasonal pattern detection, and cohort analysis all depend on querying months or years of historical data. OLAP systems store this data efficiently with compression ratios of 10x or higher, making it practical to keep complete histories rather than just recent records.
Dashboard and reporting needs
Executive dashboards, automated reports, and data visualization tools generate read-heavy workloads with complex joins across multiple tables. Running these queries on an OLTP database would slow down transactional processing, while OLAP systems handle the analytical load on separate infrastructure.
Can OLTP and OLAP work together
Modern data architectures combine both system types, with data flowing from operational databases to analytical platforms.
Operational analytics pipelines
Real-time ETL using change data capture replicates OLTP changes to OLAP systems with latency measured in seconds or minutes. Tools like Debezium, Kafka Connect, and cloud-native CDC services stream database changes as events, with Apache Kafka used by more than 80% of Fortune 100 companies for event streaming. This lets analytical systems stay current without querying operational databases directly, which would impact transactional performance.
Data lakehouse approach
Data lakehouse architectures like Delta Lake, Apache Iceberg, and Apache Hudi provide a unified storage layer that supports both transactional and analytical workloads, with 67% of organizations planning to run the majority of their analytics on data lakehouses within three years. These systems maintain ACID properties for updates while enabling analytical queries through columnar file formats like Parquet. The lakehouse approach reduces the need to maintain separate OLTP and OLAP copies of the same data.
Real-time HTAP engines
Hybrid Transaction/Analytical Processing (HTAP) systems handle both workload types in a single platform. They typically separate compute paths and maintain different storage representations, using row storage for transactions and columnar storage for analytics. The system synchronizes between them automatically, though this adds complexity compared to specialized databases. For a detailed comparison of pure OLAP vs HTAP architectures, see our ClickHouse vs SingleStore comparison.
Architectures that combine OLTP and OLAP in one engine
Several technical approaches blur the traditional boundaries between transactional and analytical processing.
Shared-nothing column stores
Distributed columnar databases like ClickHouse® scale horizontally and can serve both analytical scans and selective queries. While not designed for high-frequency updates, they handle append-mostly workloads with real-time ingestion effectively. Primary key indexes and data skipping techniques enable fast lookups on properly indexed data, delivering sub-second query latency for both aggregations and point queries.
In-memory hybrid tables
Some systems keep frequently accessed data in RAM and less-used data on disk, switching between row-oriented and column-oriented representations based on access patterns. This dual-format approach lets the same data serve low-latency transactional queries and high-throughput analytical scans, though it requires more memory and adds synchronization overhead.
Query acceleration layers
Caching, materialized views, secondary indexes, and pre-aggregations accelerate analytical queries on top of transactional data. Materialized views pre-compute common aggregations incrementally as new data arrives, trading storage and update overhead for faster query response times. This approach works well when you can predict which aggregations users will query most often.
Top OLAP database: ClickHouse
ClickHouse has become the go to OLAP database for real-time analytics, powered by high-throughput ingestion, columnar storage, and horizontal scalability to support high-concurrency access with low-latency.
Strengths of ClickHouse for OLAP workloads
Columnar storage, advanced compression, vectorized execution, and parallel processing make ClickHouse® exceptional for high-throughput aggregations. It routinely processes billions of rows per second on modern hardware, with compression ratios that reduce storage costs by 10x or more compared to row-oriented databases. Complex analytical queries that take minutes in traditional databases often complete in seconds with ClickHouse®.
Handling OLTP-like queries in ClickHouse
ClickHouse® supports fast point lookups through table engines like ReplacingMergeTree and primary key ordering. While it doesn't provide traditional ACID transactions with multi-row updates, it handles append-mostly workloads with real-time ingestion effectively. Tables ordered by primary key enable millisecond lookups for single records or small ranges, making ClickHouse® viable for operational analytics that blend transactional and analytical patterns.
Design patterns on Tinybird
Tinybird provides managed ClickHouse infrastructure that eliminates cluster management and operational overhead. Developers create data sources (ClickHouse tables) and pipes (SQL queries exposed as APIs) to serve both analytical and operational queries. The platform handles ingestion, replication, and API hosting automatically.
SCHEMA >
user_id String,
event_type String,
timestamp DateTime,
value Float64
ENGINE MergeTree
ENGINE_SORTING_KEY user_id, timestamp
This schema orders data by user_id and timestamp, enabling fast lookups by user while supporting efficient time-range scans for analytics.
Move fast with managed ClickHouse on Tinybird
Tinybird eliminates the complexity of running ClickHouse in production by providing fully managed infrastructure, automated scaling, and built-in API generation. The platform handles ingestion from streaming sources, manages replication and backups, and provides observability tools for query performance. You write SQL and Tinybird handles infrastructure provisioning, API endpoint hosting, authentication, and rate limiting.
Free workspace sign-up
Get started with a free Tinybird account at https://cloud.tinybird.co/signup. The free tier includes enough resources to build and test real-time analytics features without infrastructure overhead or upfront costs.
FAQs about OLTP and OLAP databases
Can you add OLAP analytics to an existing OLTP database without heavy ETL?
Yes, modern change data capture and streaming tools replicate OLTP data to OLAP systems in near real-time. Tools like Debezium capture database changes as events and stream them to analytical platforms through Kafka or similar message brokers. This maintains separation of concerns while reducing ETL complexity and latency compared to batch processing.
How do hybrid databases keep transactional integrity?
Hybrid systems use techniques like multi-version concurrency control (MVCC), snapshot isolation, and sometimes separate storage engines for different workload types. MVCC maintains ACID properties by keeping multiple versions of data, allowing readers to see consistent snapshots while writers make changes without blocking. Some systems use separate compute paths that share the same underlying storage but process queries differently based on workload type.
Is it cheaper to combine OLTP and OLAP workloads in one platform?
Consolidation can reduce infrastructure and data movement costs by eliminating ETL pipelines and duplicate storage, with enterprises reporting 56% expect more than 50% cost savings on analytics by moving to data lakehouses. However, specialized systems often deliver better price-performance for their target workloads. A single hybrid system might cost less to operate than two separate databases, but it might also run queries slower or require more expensive hardware. Evaluate total cost of ownership including development time, operational overhead, and performance SLAs before deciding whether to consolidate or maintain separate systems.