AWS Aurora Support
Fix Aurora replica lag.
Aurora readers share storage with the writer, so lag is normally a few milliseconds. When it climbs to seconds, applications read stale data, queries get cancelled on PostgreSQL, or readers restart. We find whether the writer, a reader or a query is the cause.
When You Need This
The situations where this work pays for itself.
Signs it is time
- Reads return stale data right after writes
- AuroraReplicaLag or its maximum rises during batch jobs
- Reader queries fail with conflict with recovery errors on PostgreSQL
- One reader is much slower than the others
- You use readers for reporting and see unpredictable latency
What you get
- Lag analysis tying spikes to writer jobs or reader limits
- Reader sizing and custom endpoint design
- Query and batch job changes to smooth write bursts
- Lag alarms and a read-consistency guideline for developers
How we do it
A clear, safe process you can follow along with.
1. Measure lag per reader
We chart AuroraReplicaLag and AuroraReplicaLagMaximum for each instance, together with the writer's write throughput and the reader's CPU and memory, to separate load-related lag from a single bad reader.
2. Correlate with writer activity
Large batch updates, bulk loads and heavy index maintenance on the writer create work that readers must apply to their cache. We time lag spikes against jobs and deployments.
3. Check reader capacity
A reader that is CPU bound or short of memory applies changes slowly. We compare instance classes and move heavy analytics to a bigger or dedicated reader.
4. Check long-running queries
On Aurora PostgreSQL, long queries on a reader can conflict with changes from the writer and be cancelled. We review hot_standby_feedback and max_standby_streaming_delay related settings and the queries themselves.
5. Fix routing
We use custom endpoints to isolate reporting readers from application readers, and make the app tolerate small lag or read from the writer where read-your-writes is required.
6. Verify
We rerun the workload, confirm lag stays within the target and add alarms with thresholds that match your consistency needs.
Mistakes we help you avoid
Common ways this goes wrong, and what we do instead.
Reading right after a write from a reader
Even small lag breaks read-your-writes. Route those reads to the writer.
Running reports on the same reader as the app
Heavy queries hurt latency and lag. Use a custom endpoint.
Ignoring a single outlier reader
A reader with a different class or noisy workload can lag alone.
Frequently Asked Questions
What is normal Aurora replica lag?
Because storage is shared, it is usually in the low tens of milliseconds, though it varies with load. Check your own baseline in CloudWatch.
Why do my Aurora PostgreSQL reader queries get cancelled?
A reader can cancel queries that conflict with changes replayed from the writer, such as removed row versions. Adjust settings and shorten or move long queries.
Does adding more readers reduce lag?
Not by itself. More readers spread read load, but lag comes from write volume or an overloaded reader, so size the readers first.
Want Help With Fix Aurora replica lag?
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