What are the main AWS services a Java backend developer should know?

// Spring Boot service using RDS, S3, and SQS
@Service
public class OrderService {
    private final OrderRepository repository; // RDS via JPA
    private final S3Client s3Client;
    private final SqsClient sqsClient;

    public Order createOrder(OrderRequest request) {
        var order = repository.save(
            new Order(null, request.item(), request.quantity())
        ); // Saved to RDS PostgreSQL

        // Upload order receipt PDF to S3
        s3Client.putObject(
            PutObjectRequest.builder()
                .bucket("order-receipts")
                .key("receipt-" + order.id() + ".pdf")
                .build(),
            RequestBody.fromBytes(generatePdf(order))
        );

        // Send message to SQS for async email notification
        sqsClient.sendMessage(
            SendMessageRequest.builder()
                .queueUrl("https://sqs.us-east-1.amazonaws.com/123456/notifications")
                .messageBody("{\"orderId\":" + order.id() + "}")
                .build()
        );
        return order;
    }
}