#design-patterns

Calculate running totals, rankings, and moving averages efficiently with SQL window functions. Code Snippet -- Running total of sales by date SELECT order_date, daily_sales, SUM(daily_sales) OVER ( ORDER BY order_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ) AS running_total FROM daily_sales_summary; -- 7-day moving average SELECT order_date, daily_sales, AVG(daily_sales) OVER ( ORDER…

Gradually replace legacy systems by routing traffic to new implementations incrementally. Code Snippet // API Gateway routing configuration // nginx.conf or API Gateway rules # Route new endpoints to modern service location /api/v2/orders { proxy_pass http://new-order-service:8080; } # Legacy endpoints still go to monolith location /api/orders { proxy_pass http://legacy-monolith:8080; } #…

Use domain events to decouple components and enable reactive architectures. Code Snippet // Domain Event public record OrderPlacedEvent( string OrderId, string UserId, decimal TotalAmount, DateTime PlacedAt ); // Event Publisher public interface IEventPublisher { Task PublishAsync(T @event) where T : class; } // In Order aggregate public class Order { private readonly List _events =…

Implement semantic search using text embeddings for more relevant results than keyword matching. Code Snippet from openai import OpenAI import numpy as np client = OpenAI() def get_embedding(text: str) -> list[float]: """Generate embedding for text using OpenAI.""" response = client.embeddings.create( model="text-embedding-3-small", input=text ) return response.data[0].embedding def…

Build modular, tested, documented data transformations with dbt. Code Snippet -- models/staging/stg_orders.sql WITH source AS ( SELECT * FROM {{ source('raw', 'orders') }} ), cleaned AS ( SELECT order_id, customer_id, CAST(order_date AS DATE) AS order_date, CAST(total_amount AS DECIMAL(10,2)) AS total_amount, LOWER(TRIM(status)) AS status FROM source WHERE order_id IS NOT NULL ) SELECT * FROM…

Use table partitioning to dramatically speed up queries on large datasets. Code Snippet -- PostgreSQL: Create partitioned table CREATE TABLE events ( event_id BIGSERIAL, event_date DATE NOT NULL, event_type VARCHAR(50), payload JSONB ) PARTITION BY RANGE (event_date); -- Create monthly partitions CREATE TABLE events_2024_01 PARTITION OF events FOR VALUES FROM ('2024-01-01') TO…

Eliminate heap allocations when parsing strings by using Span for memory-efficient operations. Code Snippet // Before: Creates new string allocations string input = "key=value"; string[] parts = input.Split('='); string key = parts[0]; string value = parts[1]; // After: Zero allocations with Span ReadOnlySpan span = input.AsSpan(); int index = span.IndexOf('='); ReadOnlySpan key =…