ProductServices.cs

public interface ICatalogService
{
    Task<Product> GetProductBySku(string sku);
    Task<Product> GetProductForSaleBySku(string sku);
    Task<List<Product>> GetProducts();
    Task UpdateProductInfo();
}

public interface ISalesService
{
    Task IncreasePrice(string sku, decimal price);
    Task DecreasePrice(string sku, decimal price);
}

public interface IPurchasingService
{
    Task IncreaseCost(string sku, decimal cost);
    Task DecreaseCost(string sku, decimal cost);
}

public interface IWarehouseService
{
    Task ShipProduct(string sku, Guid salesOrderId);
    Task ReceiveProduct(string sku, Guid purchaseOrderId);
    Task AdjustInventory(string sku, int quantity);
}