> For the complete documentation index, see [llms.txt](https://docs.digit.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.digit.org/health/v2.0/design/architecture/high-level-design/design-decision-log.md).

# Design Decision Log

## Sync

1. A server should be responsible to handle or offer a mechanism to handle errors once data reaches it. (Error handling mechanism is being designed by the platform).
2. Sync will be manually triggered by the user (except for automatically syncing configuration down on the first login).
3. Sync down of data is not required to support (good to have) the first rollout.
4. Sync will be done through bulk APIs.
5. Sync will send each save action performed by the field user while offline to the server to preserve an audit of actions performed by the field user.
   1. Eg: If a field user registers an individual and saves the record and then goes back to update the individual, this will result in two API calls to the server (one create and one update).
6. API response compression Gzip will be turned on for all the endpoints.
7. Unique identifier to be used between client and server:
   1. A Client will create a unique (client-generated) identifier per entity (clientReferenceId) to relate entities while operations are being performed offline and send this id to the server for creating operations.
   2. Any subsequent operations (like update, delete) will be on the server gen id, so the client has to get the server gen id by searching using the client generated id. The client will call search API with clientReferenceId and will get the server generated id. 
   3. Client will update the server-generated id into the records on the client and use the server-generated id for subsequent updates for those entities.
8. Processing on the backend will continue to be asynchronous and not changed for the health use case.

## Configurability

#### Backend

1. Search API max limit and the default limit.
2. Service details and endpoints.

#### Frontend

1. Service details and endpoints.
2. Number of entities sent to the server in bulk API calls
3. Additional fields per entity in the app.
4. The drop-down values or select options to be presented in the app for field users.
5. Configuration changes are expected to be additive for the data captured against such configuration to continue being usable.
6. Number of retries on API call failure after which the app should stop retrying.
7. Timeout for the API calls.

## Access Control

1. Access to data will be defined by the linkages of staff to the project and the corresponding boundary while respecting role-action mappings instead of the tenant-based approach.

## Data

1. All deletes are soft deletes.
2. The server is responsible to delete nested/child entities if applicable when the parent entity is deleted.
3. Undeletion is not permitted.
4. Duplicate updates do not need to be detected or filtered out. The client is responsible to send duplicate updates on entity as separate requests to server.
5. Since persistence in DIGIT is asynchronous but the sync process from the field worker app is likely to send dependent data in a short period, a cache is to be introduced against which dependent data can be validated if required while it is in the process of being persisted to the DB. This cache is exposed via the search API of the corresponding service and the caller is agnostic to whether the result was returned from the cache or database.
6. For v1, we can maintain the sequence of updates only for requests on a single entity by a single user. i.e. Updates on the same entity by multiple users will result in the last caller's updates going through.
7. To maintain the sequence of updates, a rowVersion field is introduced in every entity. Callers pass the rowVersion as received from the server. The server can detect if any out-of-sequence updates have come in and reject it / pass it to the error handling mechanism.
8. Search APIs will not return (soft) deleted data by default. If deleted data is required the includeDeleted param can be passed to the search APIs.

## Limitations

1. From the Product requirement perspective, there is no unique identification identifier,  so Platform is unable to check the uniqueness of registry entities.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.digit.org/health/v2.0/design/architecture/high-level-design/design-decision-log.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.