Serverless वर Distributed Transactions साठी Saga Pattern

By Ravindra Bagale, trainer · LinkedIn · Last updated: 2 November 2026

1. रोजचे उदाहरण: दोन counters वर trip booking

Fatima (Casablanca) train (MAD 420) नंतर hotel. Hotel full → train cancel = compensation. Global lock नाही. Payment Lambda + stock Lambda तसेच.

order workflow project मध्ये steps; DynamoDB transactions मध्ये atomic multi-item. Cross-service = saga.

2. Saga का?

हे का लागतं?

Cross-service ACID नाही. Locks = Lambda वेळ/पैसे. Saga = local commit + compensate.

हे काय आहे?

Saga = local tx + compensate. Orchestration = SFN. Choreography = events.

3. Vertical diagram

4. Orch vs choreo saga

5. How: payment+stock saga

कसं करायचं (step by step)

1. AWS names nako - reserve/charge/ship.
2. pratyek undo.
3. orderId+step keys.
4. SFN Catch chain.
5. Completed fakt shevati.
6. Failed + compensate alarms.

6. Commands + meaning

State machines yadi

aws stepfunctions list-state-machines --region ap-south-1 \
  --query 'stateMachines[].{N:name,A:stateMachineArn}' --output table

अर्थ: Mumbai madhye saga machine ahe ka te paha.

Failed execution

aws stepfunctions get-execution-history --region ap-south-1 \
  --execution-arn "$EXEC_ARN" --reverse-order --max-items 20 \
  --query 'events[?type==`TaskFailed` || type==`ExecutionFailed`]'

अर्थ: kuthla Task fail + error - compensate debug ithun.

Execution start

aws stepfunctions start-execution --region ap-south-1 \
  --state-machine-arn "$SM_ARN" \
  --name "ord-7841-$(date +%s)" \
  --input '{"orderId":"ord-7841","amountINR":2499,"sku":"MOMO-12"}'

अर्थ: Name unique; same name = juni execution.

Stop execution

aws stepfunctions stop-execution --region ap-south-1 \
  --execution-arn "$EXEC_ARN" --error "ManualStop" --cause "lab cleanup" 

अर्थ: Lab madhye loop stop; prod = alarm + runbook.

7. Compensation rules

• Success chya reverse kram.
• Compensate idempotent.
• Compensate fail then human queue.
• n zhalelya step cha undo nako.
• orderId correlation.
• Same currency refund.

8. kadhi saga nako

9. Industries

• Fintech Lagos.
• Ecommerce Pune.
• Travel Sofia.
• Healthcare SG.
• Logistics Amman.

10. Lab: paper then SFN

11. Lab - sketch nantar state machine

Org block नसेल तर ap-south-1 (Mumbai). आधी budget alert.

कसं करायचं (step by step)

1. Paper: 999 INR course - 3+3 steps.
2. Order-workflow SM ughada.
3. Test execution + Graph.
4. Fail path + history.
5. tumchya compensations liha.

Cleanup (billing थांबवा)

1. Loops thambava.
2. Lab SM delete.

12. एकाच pattern — वेगवेगळ्या industries

• Fintech (Aisha, Lagos): payment webhooks → SQS → Lambda.
• Ecommerce (Rohan, Pune): checkout API; inventory SNS fan-out.
• Healthcare (Mei, Singapore): SNS SMS; PHI + fine-grained IAM.
• EdTech (Diego, São Paulo): EventBridge nightly cleanup.
• Logistics (Fatima, Casablanca): EventBridge + saga.
• Media (Kenji, Osaka): S3 → Lambda thumbs + fan-out.
• SaaS (Priya, Bengaluru): Cognito + per-tenant partition.
• Gov (Omar, Amman): strangler fig per form route.

13. Troubleshooting checklist

1. Region confirm करा.
2. CloudWatch Logs + request id.
3. Execution role permissions.
4. DLQ + oldest message age.
5. curl -v + CORS.
6. SFN event history.
7. Linked chapter पुन्हा वाचा.
8. Cost: concurrency/retries.

14. सामान्य errors आणि fixes

प्रत्येक row = खरी चूक. Panic करण्याआधी fix वाचा.

15. FAQ

16. Interview Q&A (Beginner / Mid / Senior + MNC)

17. Tips — English, मराठी आणि हिंदी

18. Architecture decision checklist

1. User journey 5 bullets, no AWS names.
2. Sync vs async mark.
3. Failure mode.
4. Idempotency key.
5. Data from access patterns.
6. Cost 1x and 10x.
7. Quotas ap-south-1.
8. Auth decision.
9. On-call + alarm.
10. Deep chapter link.
11. मग console/IaC.

19. Copy-paste quick commands

# Region and identity
aws configure get region
aws sts get-caller-identity

# Lambda landscape
aws lambda list-functions --region ap-south-1 --max-items 20 \
  --query 'Functions[].{N:FunctionName,R:Runtime,T:Timeout,M:MemorySize}' --output table
aws lambda get-account-settings --region ap-south-1

# API Gateway (HTTP APIs)
aws apigatewayv2 get-apis --region ap-south-1 --query 'Items[].{N:Name,Id:ApiId,Ep:ProtocolType}' --output table

# Queues and topics
aws sqs list-queues --region ap-south-1
aws sns list-topics --region ap-south-1 --query 'Topics[].TopicArn'

# Event buses and state machines
aws events list-event-buses --region ap-south-1
aws stepfunctions list-state-machines --region ap-south-1 --query 'stateMachines[].name'

# DynamoDB tables (names only)
aws dynamodb list-tables --region ap-south-1

Sandbox + read-only IAM.

20. अजून industry आणि stack stories

• Fintech Lagos: webhook → SQS → idempotent ledger.
• Ecommerce Pune: throttle + fan-out.
• Healthcare SG: SNS + PHI IAM.
• EdTech: EventBridge cleanup.
• Logistics: bus + saga.
• Media: avoid recursive S3.
• SaaS: tenant partition.
• Gov: strangler peel.
• Startup: Function URL → HTTP API.
• Retail: FIFO vs Standard.

• Python: thin handlers.
• Node: async/await.
• Java: SnapStart.
• .NET: package size.
• Go: static binary.
• PHP: hybrid.

21. Glossary

22. Practice: मोठ्याने explain

1. 60s: saga pattern गोष्ट.
2. 60s: sync vs async checkout.
3. 60s: Lambda नको कधी.
4. 60s: DLQ + idempotency.
5. Record ×2.

23. Safe lab hygiene

• Tag owner+expiry.
• Budget alarm आधी.
• Read-only first.
• Cleanup.
• No secrets in env/screenshots.
• No provisioned on hello.

24. या chapter च्या links

• Compute: Lambda.
• HTTP: API Gateway.
• Data: DynamoDB.
• Messaging: SQS/SNS.
• Events: EventBridge.
• Workflows: Step Functions.
• build-* projects link.

25. Myths

26. Serverless error budget

Checkout error budget 0.1% असेल तर aggressive retries email duplicates देऊन budget जाळू शकतात. Money SLO ≠ notify SLO.

1. दोन SLOs.
2. Money retries bounded.
3. Notify best-effort.
4. Money page; notify ticket.

27. Regional notes (ap-south-1)

• Labs Mumbai.
• Feature availability.
• Data residency.
• Latency India.

28. Naming conventions

# Suggested prefixes
# Lambda:  pay-intake-prod, pay-worker-prod
# SQS:     pay-orders.fifo / pay-orders-dlq
# SNS:     pay-order-events
# EB bus:  pay.domain
# SFN:     pay-refund-saga
# DDB:     pay-orders-prod

env + domain नावात ठेवा. CloudWatch grep सोपा.

29. Pre-mortems

1. Double charge headline.
2. DLQ drain plan.
3. Cognito outage mode.
4. Runbook.

30. Currency / locale

Currencies आणि names rotate करा — global mental model.

31. Diego course (BRL)

1. BRL 189.
2. Reserve OK.
3. Charge fail.
4. Release; no welcome.
5. No orphan seat.

32. Anti-patterns

• Sleeps nako - SFN wait.
• Compensate != forward.
• Least privilege refund.
• orderId in logs.

33. Metrics

• ExecutionsFailed.
• Compensate Errors.
• RefundLatencyMs.
• Human DLQ.

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अजून cards: Ravi Sir's Cards.