In this talk, we cover the concepts of reactive microservices architecture, a set of patterns and best practices for implementing backend systems with very high scaling and availability guarantees. We show you how to implement these patterns and best practices as serverless applications using AWS technologies like AWS Lambda, Amazon API Gateway, Amazon DynamoDB, and Amazon Kinesis. In addition, we demonstrate a serverless microservice and the pitfalls to consider when running these microservices in a production environment.

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Reactive Microservices
with AWS Lambda
Lu Hong
Software Development Engineer
AWS Serverless Apps
S R V 2 0 1

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What is serverless?
https://aws.amazon.com/serverless/

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More than just AWS Lambda!
https://aws.amazon.com/serverless/

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What are reactive microservices?
https://aws.amazon.com/serverless/

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Example: Simple banking microservice

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Here are our tools for today

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Serverless API
POST /accounts
GET /accounts/{accountId}

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Traditional data access
accountId customerId type balance
1 A CHECKING $25.00
2 B SAVINGS $40.00
3 A SAVINGS $10.00
4 C CHECKING $35.00

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Traditional data access
accountId customerId type balance
1 A CHECKING $25.00
2 B SAVINGS $40.00
3 A SAVINGS $10.00
4 C CHECKING $35.00
Account account = getAccountById(1)
account.credit($25.00)

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Traditional data access
accountId customerId type balance
1 A CHECKING $25.00
2 B SAVINGS $40.00
3 A SAVINGS $10.00
4 C CHECKING $35.00
accountId customerId type balance
1 A CHECKING $50.00
2 B SAVINGS $40.00
3 A SAVINGS $10.00
4 C CHECKING $35.00
Account account = getAccountById(1)
account.credit($25.00)

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Event sourcing
sequence event
1 CREATED: {customerId:A, type:CHECKING, initialBalance:$25.00}
2 CREDITED: {amount:$25.00, creditType:DEPOSIT, refId:12345}
3 DEBITED: {amount:$10.00, debitType:WITHDRAWAL, refId:54321}
accountId: 1

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Event sourcing
sequence event
1 CREATED: {customerId:A, type:CHECKING, initialBalance:$25.00}
2 CREDITED: {amount:$25.00, creditType:DEPOSIT, refId:12345}
3 DEBITED: {amount:$10.00, debitType:WITHDRAWAL, refId:54321}
4 DEBITED: {amount:$20.00, debitType:FEE, refId:6789}
accountId: 1

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CQRS
Traditional
Command
operations
Query
operations
Command
operations
Query
operations
CQRS

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Write operations
Amazon DynamoDB Streams + Lambda
Event store
Query view
Non-primary key
query operations
Consumer
Lambda

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Serverless CQRS
Event store
Query view
GetAccountsByCustomer
Consumer
Lambda
Write operations +
GetAccountById

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Single entity, many log entries
accountId sequence event
1 1 CREATED: {customerId:A, type:CHECKING, initialBalance:$25.00}
1 2 CREDITED: {amount:$25.00, creditType:DEPOSIT, refId:12345}
1 3 DEBITED: {amount:$10.00, debitType:WITHDRAWAL, refId:54321}
1 4 DEBITED: {amount:$20.00, debitType:FEE, refId:6789}
… … …
1 536 CREDITED: {amount:$30.00, creditType:DEPOSIT, refId:5435}
1 537 DEBITED: {amount:$20.00, debitType:WITHDRAWAL, refId:1290}

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Solution: Snapshots
accountId version snapshot
1 512 {customerId:A, type:CHECKING, balance:$220.00}
1 536 {customerId:A, type:CHECKING, balance:$135.00}

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Solution: Snapshots
accountId sequence event
1 1 CREATED: {customerId:A, type:CHECKING, initialBalance:$25.00}
1 2 CREDITED: {amount:$25.00, creditType:DEPOSIT, refId:12345}
1 3 DEBITED: {amount:$10.00, debitType:WITHDRAWAL, refId:54321}
1 4 DEBITED: {amount:$20.00, debitType:FEE, refId:6789}
… … …
1 536 CREDITED: {amount:$30.00, creditType:DEPOSIT, refId:5435}
1 537 DEBITED: {amount:$20.00, debitType:WITHDRAWAL, refId:1290}
accountId version snapshot
1 512 {customerId:A, type:CHECKING, balance:$220.00}
1 536 {customerId:A, type:CHECKING, balance:$135.00}

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Event sourcing: Optimistic locking
accountId sequence event
1 1 CREATED: {customerId:A, type:CHECKING, initialBalance:$25.00}
1 2 CREDITED: {amount:$25.00, creditType:DEPOSIT, refId:12345}
1 3 DEBITED: {amount:$10.00, debitType:WITHDRAWAL, refId:54321}
sequence: 4
event: DEBITED: {amount:$20.00,
debitType:FEE, refId:6789
sequence: 4
event: DEBITED: {amount:$40.00,
debitType:WITHDRAWAL, refId:141

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Event sourcing: Optimistic locking
accountId sequence event
1 1 CREATED: {customerId:A, type:CHECKING, initialBalance:$25.00}
1 2 CREDITED: {amount:$25.00, creditType:DEPOSIT, refId:12345}
1 3 DEBITED: {amount:$10.00, debitType:WITHDRAWAL, refId:54321}
sequence: 4
event: DEBITED: {amount:$20.00,
debitType:FEE, refId:6789
sequence: 4
event: DEBITED: {amount:$40.00,
debitType:WITHDRAWAL, refId:141
OptimisticLockException

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Optimistic locking with DynamoDB
aws dynamodb put-item
--table-name BankAccountEntityEvents
--condition-expression
“attribute_not_exists(EntityId) AND
attribute_not_exists(SequenceNumber)”
...

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Launched in preview @ re:Invent 2017

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Generally available in February 2018

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Consuming applications
Lambda
Console
AWS
SDK
Serverless
Application
RepositorySearch/deploy
SAM apps
Consumers
(AWS customers)

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Consuming applications

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Consuming applications

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Consuming applications

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Publishing applications
Publisher
Console
AWS
SDK
Serverless
Application
Repository
Publish
SAM apps
Publishers
(AWS customers)

37. Thank you!
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Thank you!
© 2018, Amazon Web Services, Inc. or its affiliates. All rights reserved.
Lu Hong
Twitter: @luhong07

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