Initial commit: Custom Start Page application with authentication and DynamoDB storage

docs/task-3.1-implementation.md

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+# Task 3.1 Implementation: DynamoDB Storage Service Wrapper
+
+## Overview
+Enhanced the existing DynamoDB client from Task 2.1 with retry logic, connection pooling, transaction support, and batch operations.
+
+## Implementation Details
+
+### 1. Enhanced Client Configuration
+- **Retry Strategy**: Configured with exponential backoff and jitter
+  - Max attempts: 5
+  - Max backoff: 20 seconds
+  - Prevents thundering herd with jitter
+- **Connection Pooling**: Uses AWS SDK's default HTTP client with built-in connection pooling
+
+### 2. Transaction Support
+Implemented `TransactWriteItems` method for ACID transactions:
+- Supports multiple write operations in a single atomic transaction
+- Automatic retry on transient failures
+- Proper error handling and wrapping
+
+### 3. Batch Operations
+Implemented two batch operation methods:
+
+#### BatchGetItems
+- Retrieves multiple items in a single request
+- Automatically retries unprocessed keys with exponential backoff
+- Merges results from retry attempts
+- Max 5 retry attempts with increasing backoff (100ms → 20s)
+
+#### BatchWriteItems
+- Writes multiple items in a single request
+- Automatically retries unprocessed items with exponential backoff
+- Max 5 retry attempts with increasing backoff (100ms → 20s)
+
+### 4. Standard Operations
+Wrapped standard DynamoDB operations with automatic retry:
+- `PutItem` - Put a single item
+- `GetItem` - Get a single item
+- `UpdateItem` - Update a single item
+- `DeleteItem` - Delete a single item
+- `Query` - Query items
+
+All operations include proper error handling and wrapping.
+
+### 5. Comprehensive Testing
+Created `dynamodb_test.go` with tests for:
+- Client initialization
+- Transaction operations
+- Batch get operations
+- Batch write operations
+- Put and get operations
+- Update operations
+- Delete operations
+- Query operations
+
+Tests include:
+- Automatic skip when DynamoDB is not available
+- Helper function for test setup with dummy AWS credentials
+- Table creation and cleanup helpers
+- Verification of all operations
+
+## Files Modified/Created
+
+### Modified
+- `internal/storage/dynamodb.go` - Enhanced with retry logic, transactions, and batch operations
+
+### Created
+- `internal/storage/dynamodb_test.go` - Comprehensive test suite
+- `internal/storage/README.md` - Documentation for the storage service
+- `docs/task-3.1-implementation.md` - This implementation document
+
+## Requirements Addressed
+
+✅ **Requirement 8.1**: Immediate persistence with reliable operations
+✅ **Requirement 8.8**: Efficient scaling through batch operations and connection pooling
+✅ **Design**: Retry logic with exponential backoff
+✅ **Design**: Transaction support (TransactWrite)
+✅ **Design**: Batch operations (BatchGet, BatchWrite)
+✅ **Design**: Connection pooling
+
+## Testing
+
+### Running Tests
+```bash
+# Start DynamoDB Local
+docker-compose up -d
+
+# Run all storage tests
+go test -v ./internal/storage
+
+# Run specific tests
+go test -v ./internal/storage -run TestTransactWriteItems
+```
+
+### Test Coverage
+- ✅ Client initialization with retry configuration
+- ✅ Transaction writes with multiple items
+- ✅ Batch get with multiple items
+- ✅ Batch write with multiple items
+- ✅ Single item operations (Put, Get, Update, Delete)
+- ✅ Query operations
+- ✅ Graceful skip when DynamoDB unavailable
+
+## Usage Example
+
+```go
+// Create client
+ctx := context.Background()
+client, err := storage.NewDynamoDBClient(ctx, "http://localhost:8000")
+if err != nil {
+    log.Fatal(err)
+}
+
+// Transaction example
+err = client.TransactWriteItems(ctx, &dynamodb.TransactWriteItemsInput{
+    TransactItems: []types.TransactWriteItem{
+        {
+            Put: &types.Put{
+                TableName: aws.String("MyTable"),
+                Item: map[string]types.AttributeValue{
+                    "id": &types.AttributeValueMemberS{Value: "item1"},
+                },
+            },
+        },
+    },
+})
+
+// Batch write example
+err = client.BatchWriteItems(ctx, &dynamodb.BatchWriteItemInput{
+    RequestItems: map[string][]types.WriteRequest{
+        "MyTable": {
+            {
+                PutRequest: &types.PutRequest{
+                    Item: map[string]types.AttributeValue{
+                        "id": &types.AttributeValueMemberS{Value: "item1"},
+                    },
+                },
+            },
+        },
+    },
+})
+
+// Batch get example
+output, err := client.BatchGetItems(ctx, &dynamodb.BatchGetItemInput{
+    RequestItems: map[string]types.KeysAndAttributes{
+        "MyTable": {
+            Keys: []map[string]types.AttributeValue{
+                {"id": &types.AttributeValueMemberS{Value: "item1"}},
+            },
+        },
+    },
+})
+```
+
+## Next Steps
+
+This enhanced storage service is now ready to be used by:
+- Task 3.2: Data model implementations
+- Task 3.3: Table schema creation
+- All future tasks requiring DynamoDB operations
+
+The retry logic, transaction support, and batch operations provide a solid foundation for building scalable, reliable data access patterns.