System Architecture Ideas

from https://mail.google.com/mail/u/0/#inbox/FMfcgzQgLXlDXHVjLrzhRSVJqSvFWVzj

How DoorDash Launches a New Country in One Week

ByteByteGo Apr 21, 2026

This modular layered architecture, inspired by the DoorDash global expansion model, transitions from hard-coded “if/else” logic to a plug-and-play ecosystem. Below is a detailed explanation of the architecture, applied to a global financial education and analysis tool focusing on Canada, the USA, and England.

The Three-Layer Architecture

The system is defined by three distinct layers that separate “where to go” from “what to do”.

1. The Orchestrator (The Traffic Cop)

This is the entry point. It contains no business logic. Instead, it looks at the context of the user (e.g., country: "Canada") and routes them to the correct Workflow Definition.

2. Workflow Definitions (The Lego Instructions)

A workflow is an ordered list of references to specific step modules. It defines the journey for a specific market. For example:

• Canada Workflow: [Identity_Verification] -> [Tax_Residency_Check] -> [TFSA_Analysis] -> [Risk_Profile].
• USA Workflow: [Identity_Verification] -> [Tax_Residency_Check] -> [401k_IRA_Analysis] -> [Risk_Profile].
• England Workflow: [Identity_Verification] -> [Tax_Residency_Check] -> [ISA_SIPP_Analysis] -> [Risk_Profile].

3. Step Modules (The Lego Bricks)

These are self-contained units that perform a single task. They do not know which workflow they are in or which step comes next. They communicate through a standardized interface contract, which includes methods to process the step and check for completion.

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Architectural Visual & Regional Implementation

The following diagram illustrates how the system routes a user through the layers based on their country.

[ USER REQUEST ]
       |
       ▼
+---------------------------------------+
|        LAYER 1: ORCHESTRATOR          | (Routes based on Country Context)
+----------+------------+---------------+
           |            |
           |            +-----------------------+
           ▼                                    ▼
+-----------------------+           +-----------------------+           +-----------------------+
| LAYER 2: CANADA WF    |           | LAYER 2: USA WF       |           | LAYER 2: ENGLAND WF   |
| (Workflow Definition) |           | (Workflow Definition) |           | (Workflow Definition) |
+----------+------------+           +----------+------------+           +----------+------------+
           |                                   |                                   |
           ▼                                   ▼                                   ▼
+-----------------------+           +-----------------------+           +-----------------------+
| LAYER 3: STEP MODULES |           | LAYER 3: STEP MODULES |           | LAYER 3: STEP MODULES |
| [Identity Check]      |           | [Identity Check]      |           | [Identity Check]      |
| [Tax: CRA/Federal]    |           | [Tax: IRS/State]      |           | [Tax: HMRC/UK]        |
| [Product: TFSA]       |           | [Product: 401k/IRA]   |           | [Product: ISA/SIPP]   |
+-----------------------+           +-----------------------+           +-----------------------+
           |                                   |                                   |
           +-----------------+-----------------+-----------------------------------+
                             |
                             ▼
                +-------------------------+
                |   SHARED STATUS MAP     | (JSON State: Tracks Progress)
                +-------------------------+

Core Components for Financial Localization

• Standardized Interfaces: Each team (Tax, Compliance, Investment Products) can own their specific modules. The “Investment Product” team can iterate on the 401(k) module for the USA without ever touching or risking the ISA module for England.
• Composite & Conditional Steps: You can group granular steps (like “Profile,” “Address,” and “Income”) into a single “Onboarding Details” composite step. In Canada, you might use a conditional step for Service-Area Mapping to determine local tax variances (like HST vs. GST).
• Centralized State (The Status Map): Instead of checking multiple database tables, a single Status Map (a JSON object) tracks exactly where the user is. For instance, if a user in England completes the “Identity Check” but stops before “ISA Analysis,” the map stores that progress atomically, allowing the user to resume exactly where they left off.

Why This Scales

This architecture allows you to launch in a new country with minimal new code. For example, after building the tool for Canada and the USA, launching in England might only require creating one or two new modules for UK-specific tax laws, while reusing the “Identity Check” and “Risk Profile” modules developed for previous markets.

Would you like me to create an infographic that visualizes the “Status Map” JSON structure for these three countries?