Implementation Strategies

// Pseudocode for scatter-gather query
List<Partition> partitions = getPartitions();
List<Future<Result>> futures = new ArrayList<>();

// Scatter phase: query all partitions
for (Partition partition : partitions) {
    futures.add(executorService.submit(() -> {
        return partition.executeQuery(query);
    }));
}

// Gather phase: collect and combine results
List<Result> results = new ArrayList<>();
for (Future<Result> future : futures) {
    results.add(future.get());
}

return combineResults(results);

-- Example of a query that benefits from partition pruning
SELECT * FROM sales 
WHERE sale_date BETWEEN '2025-01-01' AND '2025-01-31';

-- If sales is partitioned by month, only the January partition is accessed

// DynamoDB Global Secondary Index example
CreateTableRequest createTableRequest = new CreateTableRequest()
    .withTableName("Orders")
    .withKeySchema(
        new KeySchemaElement("customerId", KeyType.HASH),
        new KeySchemaElement("orderId", KeyType.RANGE))
    .withAttributeDefinitions(
        new AttributeDefinition("customerId", ScalarAttributeType.S),
        new AttributeDefinition("orderId", ScalarAttributeType.S),
        new AttributeDefinition("orderStatus", ScalarAttributeType.S),
        new AttributeDefinition("orderDate", ScalarAttributeType.S))
    .withGlobalSecondaryIndexes(
        new GlobalSecondaryIndex()
            .withIndexName("OrderStatusIndex")
            .withKeySchema(
                new KeySchemaElement("orderStatus", KeyType.HASH),
                new KeySchemaElement("orderDate", KeyType.RANGE))
            .withProjection(new Projection().withProjectionType(ProjectionType.ALL))
            .withProvisionedThroughput(new ProvisionedThroughput(5L, 5L)));

// Pseudocode for Saga pattern
public void createOrderSaga(Order order) {
    try {
        // Step 1: Create order in Orders partition
        String orderId = orderService.createOrder(order);
        
        try {
            // Step 2: Reserve inventory in Inventory partition
            inventoryService.reserveItems(orderId, order.getItems());
            
            try {
                // Step 3: Process payment in Payments partition
                paymentService.processPayment(orderId, order.getPaymentDetails());
                
                // All steps succeeded
                orderService.completeOrder(orderId);
            } catch (Exception e) {
                // Compensating transaction for Step 2
                inventoryService.releaseItems(orderId);
                // Compensating transaction for Step 1
                orderService.cancelOrder(orderId);
                throw e;
            }
        } catch (Exception e) {
            // Compensating transaction for Step 1
            orderService.cancelOrder(orderId);
            throw e;
        }
    } catch (Exception e) {
        // Handle saga failure
        throw new SagaFailedException("Failed to create order", e);
    }
}