Introduction
There is a lot to be excited about in SQL Server 2025! When thinking about features that may not get as much attention as others, yet will make a real difference in the lives of DBAs, I have selected my top 5 enhancements for SQL Server 2025. These improvements may not make the headlines, but they address pain points we’ve all experienced as DBAs. Please let me know if I’ve left any of your favorites off the list.
1. High-Availability That Recovers Its Balance Faster
Failovers today succeed quickly only when the failure mode is obvious. In the 2025 engine the health-detection code watches for subtle I/O starvation and memory-broker dead-ends, letting a replica admit defeat before connections pile up. Once the secondary steps up, asynchronous page-request dispatching keeps redo busy while user traffic flows, shaving seconds—or minutes—off brownouts without extra knobs for the DBA to tweak.
2. Accelerated Database Recovery for tempdb
Tempdb has always been the wildcard in rollback math; short-lived objects can pin the log for far too long. By allowing ADR to run inside tempdb itself, 2025 brings the same instantaneous rollback you enjoy in user databases to #tables, table variables, and engine work-tables. The change feels prosaic until the first time a fat reporting query is cancelled and vanishes from sys.dm_tran_active_transactions instead of lingering for half an hour.
3. Tempdb on tmpfs for Linux Deployments
Latency in tempdb spills often traces back to the storage layer. If you’re running on bare-metal or Kubernetes, SQL Server 2025 lets you relocate tempdb files onto a RAM-backed tmpfs filesystem. Because tempdb is rebuilt at startup there is no durability concern, yet hash joins, sorts, and index rebuilds see storage latency drop to near-zero. It’s a one-liner in a Helm chart, and still keeps user databases on safe, persistent volumes.
4. Transaction-ID Locking Eases Peak-Hour Contention
Blocker trees seldom start with a single massive query; they start with a hot table and thousands of tiny writers. TID-based locking changes the granularity at which the engine tracks row locks, giving each writer its own slot instead of climbing the object hierarchy. Early benchmark traces show lock-manager memory dropping and LCK_M_IX wait time sliding downward on ticket-sale style workloads—no code changes required.
5. Practical IQP Enhancements You’ll Notice Immediately
Intelligent Query Processing keeps evolving, but the 2025 release zeroes in on improvements you can feel during everyday workloads.
- Cardinality-estimation feedback for expressions learns from prior runs and refines row estimates for calculated columns, CASE expressions, and implicit conversions.
- Degree-of-Parallelism feedback (now on by default) ships on by default and automatically converges on the right MAXDOP for recurrent statements—no trace flags or manual tuning.
- Optimized Halloween protection rewires spool logic to slash tempdb writes during wide updates and deletes.
- Query Store on readable secondaries (now on by default) means you no longer lose performance history once a replica is promoted.
ABORT_QUERY_EXECUTIONhint lets you blacklist non-critical, high-cost queries before they ever run during peak hours.
Fewer surprise spills and steadier CPU mean less time spent wrestling with plan guides.
Conclusion
SQL Server 2025 tackles long-standing operational headaches: sluggish failovers, runaway tempdb usage, lock storms, and brittle query plans. If you run on-prem instances or SQL Server on Azure VMs, these five changes should translate into quieter pagers, smoother maintenance windows, and more bandwidth for forward-looking projects.
You can find a complete list of changes in the SQL Server 2025 Preview on the Official Microsoft page.
Preview Notice Features described here reflect the SQL Server 2025 public preview as of May 2025 and could change before general availability. Please refer to the final release notes and documentation for accurate information on the SQL Server 2025 RTM release.