Managing AWS Dynamodb Deep

AWS DynamoDB Deep-Dive Skill

Deep analysis of DynamoDB tables, capacity planning, index health, and operational metrics.

MANDATORY: Discovery-First Pattern

Always list tables and get basic descriptions before deep-diving.

Phase 1: Discovery

#!/bin/bash
export AWS_PAGER=""

echo "=== DynamoDB Tables ==="
TABLES=$(aws dynamodb list-tables --output text --query 'TableNames[]')
echo "$TABLES" | tr '\t' '\n'

echo ""
echo "=== Table Summary ==="
for table in $TABLES; do
  aws dynamodb describe-table --table-name "$table" --output text \
    --query "Table.[TableName,TableStatus,BillingModeSummary.BillingMode,ItemCount,TableSizeBytes,GlobalSecondaryIndexes[].IndexName|join(',',@)]" &
done
wait

echo ""
echo "=== Auto-Scaling Targets ==="
aws application-autoscaling describe-scalable-targets --service-namespace dynamodb --output text \
  --query 'ScalableTargets[].[ResourceId,ScalableDimension,MinCapacity,MaxCapacity]' 2>/dev/null | head -20

Phase 2: Analysis

#!/bin/bash
export AWS_PAGER=""

END_TIME=$(date -u +"%Y-%m-%dT%H:%M:%S")
START_TIME=$(date -u -d "7 days ago" +"%Y-%m-%dT%H:%M:%S" 2>/dev/null || date -u -v-7d +"%Y-%m-%dT%H:%M:%S")

echo "=== Throttle Events (7d) ==="
for table in $(aws dynamodb list-tables --output text --query 'TableNames[]'); do
  {
    read_throttle=$(aws cloudwatch get-metric-statistics --namespace AWS/DynamoDB --metric-name ReadThrottleEvents \
      --dimensions Name=TableName,Value="$table" \
      --start-time "$START_TIME" --end-time "$END_TIME" --period 604800 --statistics Sum \
      --output text --query 'Datapoints[0].Sum')
    write_throttle=$(aws cloudwatch get-metric-statistics --namespace AWS/DynamoDB --metric-name WriteThrottleEvents \
      --dimensions Name=TableName,Value="$table" \
      --start-time "$START_TIME" --end-time "$END_TIME" --period 604800 --statistics Sum \
      --output text --query 'Datapoints[0].Sum')
    printf "%s\tReadThrottles:%s\tWriteThrottles:%s\n" "$table" "${read_throttle:-0}" "${write_throttle:-0}"
  } &
done
wait

echo ""
echo "=== Consumed vs Provisioned Capacity ==="
for table in $(aws dynamodb list-tables --output text --query 'TableNames[]'); do
  {
    consumed_read=$(aws cloudwatch get-metric-statistics --namespace AWS/DynamoDB --metric-name ConsumedReadCapacityUnits \
      --dimensions Name=TableName,Value="$table" \
      --start-time "$START_TIME" --end-time "$END_TIME" --period 604800 --statistics Average \
      --output text --query 'Datapoints[0].Average')
    consumed_write=$(aws cloudwatch get-metric-statistics --namespace AWS/DynamoDB --metric-name ConsumedWriteCapacityUnits \
      --dimensions Name=TableName,Value="$table" \
      --start-time "$START_TIME" --end-time "$END_TIME" --period 604800 --statistics Average \
      --output text --query 'Datapoints[0].Average')
    printf "%s\tAvgReadCU:%.1f\tAvgWriteCU:%.1f\n" "$table" "${consumed_read:-0}" "${consumed_write:-0}"
  } &
done
wait

echo ""
echo "=== GSI Status ==="
for table in $(aws dynamodb list-tables --output text --query 'TableNames[]'); do
  aws dynamodb describe-table --table-name "$table" --output text \
    --query "Table.GlobalSecondaryIndexes[].[\"$table\",IndexName,IndexStatus,ItemCount,Projection.ProjectionType]" 2>/dev/null &
done
wait

echo ""
echo "=== Streams & TTL ==="
for table in $(aws dynamodb list-tables --output text --query 'TableNames[]'); do
  {
    stream=$(aws dynamodb describe-table --table-name "$table" --output text \
      --query 'Table.StreamSpecification.StreamEnabled')
    ttl=$(aws dynamodb describe-time-to-live --table-name "$table" --output text \
      --query 'TimeToLiveDescription.TimeToLiveStatus')
    printf "%s\tStream:%s\tTTL:%s\n" "$table" "${stream:-disabled}" "${ttl:-DISABLED}"
  } &
done
wait

echo ""
echo "=== Backups ==="
aws dynamodb list-backups --output text \
  --query 'BackupSummaries[].[TableName,BackupName,BackupStatus,BackupCreationDateTime,BackupType]' | head -10

echo ""
echo "=== Contributor Insights ==="
for table in $(aws dynamodb list-tables --output text --query 'TableNames[]'); do
  aws dynamodb describe-contributor-insights --table-name "$table" --output text \
    --query "[TableName,ContributorInsightsStatus]" 2>/dev/null &
done
wait

Output Format

• Target ≤50 lines per output
• Use --output text --query for all commands
• Tab-delimited fields: TableName, Metric, Value
• Aggregate capacity metrics as averages over the period
• Never dump full table items -- show metadata and metrics only

Anti-Hallucination Rules

1. NEVER assume resource names — always discover via CLI/API in Phase 1 before referencing in Phase 2.
2. NEVER fabricate metric names or dimensions — verify against the service documentation or --help output.
3. NEVER mix CLI commands between service versions — confirm which version/API you are targeting.
4. ALWAYS use the discovery → verify → analyze chain — every resource referenced must have been discovered first.
5. ALWAYS handle empty results gracefully — an empty response is valid data, not an error to retry.

Counter-Rationalizations

Common Pitfalls

• Billing mode: PAY_PER_REQUEST vs PROVISIONED -- capacity metrics differ significantly
• GSI throttling: GSIs have independent capacity -- throttled GSIs can cause table-level write throttling
• Hot partitions: Use Contributor Insights to identify hot partition keys
• On-demand scaling: On-demand tables can throttle if traffic exceeds 2x previous peak within 30 minutes
• Auto-scaling delay: Auto-scaling reacts to CloudWatch alarms with ~5 minute delay -- not instant
• Item size: Max 400KB per item -- check AverageItemSize from table description
• Stream retention: DynamoDB Streams retain data for 24 hours only -- process events promptly
• Backup types: AWS_BACKUP (managed by AWS Backup), SYSTEM (continuous backups), USER (on-demand)