Messaging, business applications and customer enablement: EventBridge, SNS, SQS, Connect, SES and AWS Support

Why this matters

Modern applications are rarely one program. An online shop is a web front end, a payment system, a warehouse system and an email sender, all of which need to pass information to each other without falling over when one of them is slow. The services that carry those messages decide whether a traffic spike means lost orders or simply a short delay. A junior engineer who knows the difference between a queue and a notification can design a system that bends instead of breaking.

The same lesson reaches people well outside engineering. A customer service manager may be choosing a contact centre. A marketing team may need to send millions of emails. A finance lead may be asked whether the company's support plan covers a production outage. Each of these is a service decision with a clear AWS answer.

This lesson covers three groups: the messaging services that connect parts of an application, two ready-made business applications, and the support available from AWS itself.

The lesson

Application integration: EventBridge, SNS and SQS

The key idea is decoupling. In a tightly coupled system, one component calls another directly and waits; if the second is slow or down, the first fails too. In a decoupled system, components exchange messages through a service in the middle, so each can work at its own pace and fail without taking the others with it. Three services do this in different ways.

Amazon Simple Queue Service (Amazon SQS) is a fully managed message queue. A producer puts a message on the queue, and the queue holds it. A consumer, such as a back-end worker, polls the queue when it is ready, takes the message, processes it and deletes it. If orders arrive faster than workers can handle them, they wait safely in the queue instead of being lost. Standard queues offer very high throughput; FIFO (first-in, first-out) queues keep messages in strict order and process each one exactly once, for cases where order matters.

Amazon Simple Notification Service (Amazon SNS) is a publish and subscribe (pub/sub) service. A publisher sends a message once to a topic, and SNS immediately pushes a copy to every subscriber of that topic. Subscribers can be applications, such as SQS queues, Lambda functions and HTTP endpoints, or people, through SMS text messages, email and mobile push notifications. SNS does not keep a message for someone to collect later.

The difference fits in one sentence: SNS pushes each message to every subscriber at once; SQS stores each message until one consumer pulls it. Reversing the two is the classic error.

They are often combined in the fan-out pattern. An order event is published once to an SNS topic, and several SQS queues subscribe to it, one each for billing, shipping and analytics. Every system gets its own copy and processes it at its own speed.

Amazon EventBridge is a serverless event bus. An event is a record that something happened: an EC2 instance changed state, a file arrived, a customer signed up. EventBridge receives events from AWS services, from custom applications and from third-party SaaS (software as a service) partners. Rules match the content of each event and route it to the right targets, such as Lambda functions, SQS queues, SNS topics or Step Functions workflows. EventBridge can also invoke targets on a schedule, using cron or rate expressions, so a Lambda function can run every night with no server to keep a clock.

AWS Step Functions, also in scope, is different again. It orchestrates a multi-step process as a visual workflow, with steps in sequence, branches, error handling and automatic retries. SQS can pass messages between functions, but it knows nothing about the process as a whole; Step Functions does.

Business applications: Amazon Connect and Amazon SES

These are complete applications rather than building blocks.

Amazon Connect is a cloud contact centre. It provides phone numbers, an IVR (interactive voice response, the "press 1 for billing" menu), routing of each call or chat to the right human agent, and tools for those agents, without the customer buying telephone hardware. It is paid for as it is used. It can work with Amazon Lex, covered in lesson 20, so callers can speak naturally to the menu instead of pressing keys.

Amazon Simple Email Service (Amazon SES) is a service for sending email at scale from applications: transactional email, such as order confirmations and password resets, and marketing email, such as newsletters, with the company's own HTML designs. It can also receive email. SES is built for sending to large customer lists and includes features that help messages reach the inbox.

Customer enablement services (for example, AWS Support)

Customer enablement is the AWS category for helping customers succeed, and AWS Support is its central service. Lesson 25 covers the plans and resources in depth; the outline here is enough to recognise the choices.

• Basic Support is included for every AWS customer at no extra cost. It covers customer service for account and billing questions, and access to documentation, whitepapers, the AWS re:Post community, the AWS Health Dashboard and a core set of AWS Trusted Advisor checks. It does not include technical support cases with AWS engineers.
• The paid plans the guide names are AWS Business Support+, AWS Enterprise Support and AWS Unified Operations. They add technical support from AWS engineers, with more proactive guidance and faster response at each step up. AWS Unified Operations is the most comprehensive, adding a dedicated team of AWS experts for mission-critical workloads.

Support cases, whether for billing or, on a paid plan, for technical problems, are opened in the AWS Support Center. Response times and prices differ by plan and change over time, so check the current figures on the AWS Support plans page rather than memorising them.

One more channel is easy to miss. The AWS Trust and Safety team handles reports that AWS resources are being used for abuse: spam, port scanning, denial-of-service attacks or hosting malicious content. If an AWS IP address is attacking a company, this team, not a support plan, is where the report goes.

Choosing a service for messages, alerts and notifications

Match the shape of the delivery:

• One message to many recipients, immediately, including people by SMS or email: SNS. A CloudWatch alarm that must text and email the whole operations team at once is the standard case.
• Hold work until a worker is free, absorbing spikes: SQS.
• Each of several systems needs its own copy to process at its own pace: SNS plus SQS in a fan-out.
• React to events from AWS services or SaaS applications, routed by their content, or run something on a schedule: EventBridge.
• Coordinate steps with branching and retries: Step Functions.
• Designed email to customers at scale: SES. SNS can send a plain email notification to people who have subscribed to a topic, but it is not a newsletter or bulk email tool.

Choosing a business application

The two business applications are rarely confused with each other, but each has a decoy. A scenario about customers phoning in, hearing a voice menu and reaching an agent is Amazon Connect; Amazon Polly can supply a synthetic voice, but it is not a contact centre. A scenario about sending email to customers, whether receipts or campaigns, is Amazon SES; SNS sends alerts, not designed email. The word "contact centre" or "call centre" points to Connect; the words "newsletter", "transactional email" or "bulk email" point to SES.

Choosing the right kind of support

Work out what kind of help is needed:

• A billing or account question: any customer, including on Basic Support, can open a case in Support Center.
• A technical problem needing AWS engineers: a paid plan, such as AWS Business Support+, is required. A company on Basic Support must upgrade first.
• Mission-critical workloads needing the most comprehensive, proactive help: AWS Unified Operations, with AWS Enterprise Support the strong tier below it.
• Self-service answers: documentation, the AWS Knowledge Center and AWS re:Post, available to everyone.
• Abuse coming from AWS resources: the AWS Trust and Safety team.
• Help designing or delivering a project, rather than fixing a fault: AWS Professional Services, AWS solutions architects or an AWS Partner, covered in lesson 26.

What the exam is really asking

Questions in this area usually turn on a single verb. "Push" or "notify" points to SNS; "queue", "hold" or "decouple" points to SQS; "route events" or "schedule" points to EventBridge; "orchestrate" points to Step Functions. For people rather than programs, "call centre" means Connect and "email campaign" means SES. For support, first separate billing help from technical help, then match the depth of help to the plan.