This content originally appeared on DEV Community and was authored by Vishad Patel
Most developers working with Hibernate rely on the default Session, which comes with a built-in persistence context (a first-level cache). This persistence context is great for tracking loaded entities, detecting changes, and managing dirty checking—all essential for read-write operations.
But here’s the catch: for read-intensive workloads like reporting dashboards, analytics queries, or large-scale data exports, this persistence context becomes a performance bottleneck. Hibernate ends up doing a lot of unnecessary bookkeeping even though we’re not modifying any data.
That’s where read-only sessions come into play.
🚀 How Read-Only Sessions Work
By enabling read-only mode (session.setDefaultReadOnly(true)), Hibernate can skip several expensive operations:
- No snapshot tracking → Hibernate won’t keep a copy of the original entity state.
- No dirty checking → The session doesn’t scan for modifications before committing.
- Reduced memory footprint → Entities aren’t held in the persistence context long-term.
In short, Hibernate treats your session as a fire-and-forget data reader, rather than preparing for updates that will never happen.
Here’s the optimal way to implement it:
Session session = sessionFactory
.withOptions()
.flushMode(FlushMode.MANUAL) // Gives you full control
.readOnly(true)
.openSession();
try {
List<Employee> employees = session
.createQuery("FROM Employee e WHERE e.department = :dept", Employee.class)
.setParameter("dept", "SALES")
.setHint("org.hibernate.readOnly", true) // Explicit for clarity
.setTimeout(30) // Safety: prevent long-running queries
.list();
return employees;
} finally {
session.close(); // Always clean up resources
}
📊 Real-World Production Impact
To see why this matters, let’s look at a fintech system processing 50,000+ transactions per hour.
After implementing read-only sessions for reporting endpoints, the team observed:
✅ 40% lower heap memory usage – no persistence context overhead.
✅ Response time dropped from 1.5s → 300ms – dirty checking bypassed.
✅ 25% fewer GC pauses – fewer objects retained in memory.
That’s not just a micro-optimization; it’s a production-grade improvement that directly impacts customer experience.
🛠 When to Use Read-Only Sessions
Read-only sessions aren’t meant for every use case. They shine when you’re only fetching data, such as:
- Reporting and analytics dashboards
- Data export functionality (Excel, CSV, PDFs)
- Loading reference data (countries, currencies, user roles, etc.)
- Any operation where no entity modifications are required
⚡ Final Thoughts
If you’re building reporting-heavy applications or handling large-scale read queries, relying on Hibernate’s default session can silently eat up memory and CPU.
By switching to read-only sessions, you not only cut down on unnecessary overhead but also unlock significant performance gains that your end-users will notice immediately.
This small configuration tweak can be the difference between laggy dashboards and snappy real-time insights.
👉 If you found this helpful, consider following me for more Hibernate and backend performance optimization tips. You can also check out my original article here: 7 Hibernate Performance Techniques That Saved Our Production Apps
This content originally appeared on DEV Community and was authored by Vishad Patel
Vishad Patel | Sciencx (2025-09-06T12:00:14+00:00) Hibernate Performance: Boost High-Volume Queries with Read-Only Sessions. Retrieved from https://www.scien.cx/2025/09/06/hibernate-performance-boost-high-volume-queries-with-read-only-sessions/
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