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Fix AWS RDS Aurora Global Database Replication Lag

Resolve Aurora Global Database replication lag by optimizing network latency, instance sizing, and write throughput patterns.

Published: Apr 1, 20266 min readBy FixWikiHub Editorial Team

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Introduction

Aurora Global Database replicates data from a primary Region to secondary Regions using dedicated infrastructure. When replication lag increases, secondary Region databases serve stale data, affecting disaster recovery readiness and cross-Region read performance.

Symptoms

Replication lag metrics high:

```bash $ aws cloudwatch get-metric-statistics \ --namespace AWS/RDS \ --metric-name AuroraGlobalDBReplicationLag \ --dimensions Name=GlobalClusterIdentifier,Value=my-global-cluster \ --statistics Maximum \ --period 60

# Lag in milliseconds, should be < 1000ms (1 second) # If > 5000ms (5 seconds), investigate ```

Stale reads in secondary Region:

```sql -- On primary Region SELECT MAX(id) FROM orders; -- Returns 10000

-- On secondary Region (with lag) SELECT MAX(id) FROM orders; -- Returns 9500 (missing 500 rows) ```

Replication status alerts:

```bash $ aws rds describe-global-clusters \ --global-cluster-identifier my-global-cluster \ --query 'GlobalClusters[*].GlobalClusterMembers[*].[Region,IsWriter,ReplicationLag]'

# Secondary regions showing high lag values ```

Common Causes

1.Network latency - High latency between regions
2.Write throughput too high - More writes than replication can process
3.Instance size mismatch - Secondary smaller than primary
4.Binlog processing bottleneck - Storage I/O limitations
5.Cross-region bandwidth limits - AWS infrastructure throttling
6.Large transactions - Big batch operations causing lag spikes
7.Storage latency - Secondary storage performance issues

Step-by-Step Fix

1.Check logs for specific error messages
2.Verify configuration settings
3.Test network connectivity
4.Review recent changes
5.Apply corrective action
6.Verify the fix

Step 1: Monitor Replication Lag

```bash # Get replication lag metrics aws cloudwatch get-metric-statistics \ --namespace AWS/RDS \ --metric-name AuroraGlobalDBReplicationLag \ --dimensions Name=GlobalClusterIdentifier,Value=my-global-cluster \ --statistics Maximum,Average \ --period 60 \ --start-time $(date -d '1 hour ago' +%s)000

# Normal: < 1 second # Warning: 1-5 seconds # Critical: > 5 seconds

# Set up alert aws cloudwatch put-metric-alarm \ --alarm-name aurora-global-replication-lag \ --namespace AWS/RDS \ --metric-name AuroraGlobalDBReplicationLag \ --dimensions Name=GlobalClusterIdentifier,Value=my-global-cluster \ --threshold 5000 \ --comparison-operator GreaterThanThreshold \ --period 60 \ --evaluation-periods 3 ```

Step 2: Check Write Throughput on Primary

```bash # Check write operations aws cloudwatch get-metric-statistics \ --namespace AWS/RDS \ --metric-name WriteIOPS \ --dimensions Name=DBClusterIdentifier,Value=my-primary-cluster \ --statistics Sum \ --period 60

# High write throughput increases lag # Global DB can replicate ~2GB/second typically ```

Step 3: Compare Instance Sizes

```bash # Check primary instance aws rds describe-db-clusters --db-cluster-identifier my-primary-cluster \ --query 'DBClusters[*].DBClusterMembers[*].[DBInstanceIdentifier,InstanceClass,IsClusterWriter]'

# Check secondary instance aws rds describe-db-clusters --db-cluster-identifier my-secondary-cluster \ --query 'DBClusters[*].DBClusterMembers[*].[DBInstanceIdentifier,InstanceClass,IsClusterWriter]'

# Secondary should match or exceed primary for best replication performance ```

Upgrade secondary if undersized:

bash

aws rds modify-db-instance \
  --db-instance-identifier my-secondary-instance \
  --db-instance-class db.r6g.2xlarge \
  --apply-immediately

Step 4: Check Network Latency

```bash # Aurora Global DB uses AWS backbone # Check typical latencies between regions: # us-east-1 to us-west-2: ~60-80ms # us-east-1 to eu-west-1: ~80-100ms # us-east-1 to ap-southeast-1: ~200-250ms

# Higher latency regions will have higher baseline lag # Choose regions with lower latency for lower lag ```

Step 5: Optimize Large Transactions

```sql -- Check for long-running transactions SELECT * FROM information_schema.innodb_trx ORDER BY trx_started ASC;

-- Large transactions cause lag spikes -- Split into smaller batches:

-- BAD: Single large transaction BEGIN; DELETE FROM logs WHERE created_at < '2024-01-01'; -- Millions of rows COMMIT;

-- GOOD: Batched transactions DELETE FROM logs WHERE created_at < '2024-01-01' LIMIT 10000; -- Repeat in batches ```

Step 6: Check Storage Performance

```bash # Check IOPS on secondary aws cloudwatch get-metric-statistics \ --namespace AWS/RDS \ --metric-name ReadIOPS \ --dimensions Name=DBInstanceIdentifier,Value=my-secondary-instance \ --statistics Maximum \ --period 60

# If hitting IOPS limits, storage may be bottleneck # Aurora storage auto-scales, but check for throttling ```

Step 7: Monitor Binlog Processing

```bash # Check binlog metrics aws cloudwatch get-metric-statistics \ --namespace AWS/RDS \ --metric-name BinLogDiskUsage \ --dimensions Name=DBInstanceIdentifier,Value=my-primary-instance \ --statistics Maximum \ --period 60

# High binlog usage indicates replication backlog ```

Step 8: Use Appropriate Instance Types

```bash # Aurora Global DB works best with: # - Memory optimized (r6g, r6i) for large datasets # - Compute optimized (c6g) for high throughput # - Aurora optimized instances

# Upgrade instance types aws rds modify-db-instance \ --db-instance-identifier my-secondary-instance \ --db-instance-class db.r6g.2xlarge \ --apply-immediately ```

Step 9: Consider Region Selection

```bash # Regions closer together have lower lag # For US applications: # Primary: us-east-1 # Secondary: us-east-2 (~10-20ms) or us-west-2 (~60-80ms)

# For global applications: # Primary: us-east-1 # Secondary: eu-west-1, ap-southeast-1 (higher lag acceptable)

# List regions with clusters aws rds describe-global-clusters \ --global-cluster-identifier my-global-cluster \ --query 'GlobalClusters[*].GlobalClusterMembers[*].Region' ```

Step 10: Monitor Failover Readiness

```bash # Check if secondary is ready for failover aws rds describe-db-clusters \ --db-cluster-identifier my-secondary-cluster \ --query 'DBClusters[*].[Engine,EngineVersion,MultiAZ]'

# Test failover (in maintenance window) aws rds failover-global-cluster \ --global-cluster-identifier my-global-cluster \ --target-db-cluster-identifier arn:aws:rds:region:account:cluster:my-secondary-cluster

# Monitor failover time # Should complete in < 1 minute for Global DB ```

Aurora Global DB Performance Reference

Metric	Normal	Warning	Critical
Replication Lag	< 1s	1-5s	> 5s
Write Throughput	< 1GB/s	1-2GB/s	> 2GB/s
Failover Time	< 1 min	1-2 min	> 2 min

Verification

```bash # After making changes, monitor lag aws cloudwatch get-metric-statistics \ --namespace AWS/RDS \ --metric-name AuroraGlobalDBReplicationLag \ --dimensions Name=GlobalClusterIdentifier,Value=my-global-cluster \ --statistics Average \ --period 60

# Should show consistent lag < 1 second

# Test read on secondary psql -h my-secondary-cluster.cluster-xyz.region-2.rds.amazonaws.com \ -U admin -d mydb \ -c "SELECT MAX(id) FROM orders;"

# Should be close to primary (within replication lag) ```

[Fix AWS RDS Aurora Failover Slow](/articles/fix-aws-rds-aurora-failover-slow)
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Last updated: Apr 1, 2026

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Fix AWS RDS Aurora Global Database Replication Lag

Introduction

Symptoms

Common Causes

Step-by-Step Fix

Step 1: Monitor Replication Lag

Step 2: Check Write Throughput on Primary

Step 3: Compare Instance Sizes

Step 4: Check Network Latency

Step 5: Optimize Large Transactions

Step 6: Check Storage Performance

Step 7: Monitor Binlog Processing

Step 8: Use Appropriate Instance Types

Step 9: Consider Region Selection

Step 10: Monitor Failover Readiness

Aurora Global DB Performance Reference

Verification

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FixWikiHub Editorial Team

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Fix AWS RDS Aurora Global Database Replication Lag

Introduction

Symptoms

Common Causes

Step-by-Step Fix

Step 1: Monitor Replication Lag

Step 2: Check Write Throughput on Primary

Step 3: Compare Instance Sizes

Step 4: Check Network Latency

Step 5: Optimize Large Transactions

Step 6: Check Storage Performance

Step 7: Monitor Binlog Processing

Step 8: Use Appropriate Instance Types

Step 9: Consider Region Selection

Step 10: Monitor Failover Readiness

Aurora Global DB Performance Reference

Verification

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