Instructions to use Feature flag service

 # Feature Flag Service Documentation
## 📚 Introduction
- What is a Feature Flag?
- Why this service exists (e.g., "Control feature rollout, A/B testing, kill switches").
- Brief on how it works conceptually (toggle on/off for users or all).
- Having a centralised place to control all feature flags, instead of managing their rollout in service configs / ENVs.


## ⚙️ Architecture Overview
Include a diagram if possible.

a. AWS Services Used:
- AWS API gateway -> (for routing requests to different lambdas)
- AWS Systems manager -> to store the public key safely
- AWS lambda
- AWS DynamoDb
- Cloudwatch -> for monitoring + APM (if enabled X-ray tracing)

## 🛠️ Using the Feature Flag API
###  1. ➕ Create a feature flag
<details>
 
 #### API Endpoint
```
POST `/feature-flags`
```

#### Request object
```
{
    "name": "Test-flag-via-postman",
    "description": "Feature flag created via postman",
    "userId":"vikhyat"
}
```
#### Sucess Response object
```
{
    "data": {
        "id": "0cffec18-518a-41b2-b5e5-86604c06c38c",
        "name": "Test-flag-via-postman",
        "description": "Feature flag created via postman",
        "createdAt": 1745424103,
        "createdBy": "vikhyat",
        "updatedAt": 1745424103,
        "updatedBy": "vikhyat",
        "status": "ENABLED"
    },
    "message": "Created feature flag successfully"
}
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 2. 🔍 Get a feature flag
<details>

  #### API Endpoint
  ```
  GET `/feature-flags/{flagId}`
  ```
#### Request object

```
Empty
```
#### Path param 
```
<flagId> - uuid for identifying the feature flags
```

#### Sucess Response object
```
{
    "id": "0cffec18-518a-41b2-b5e5-86604c06c38c",
    "name": "Test-flag-via-postman",
    "description": "Feature flag created via postman",
    "status": "ENABLED",
    "createdAt": 1745424103,
    "createdBy": "vikhyat",
    "updatedAt": 1745424103,
    "updatedBy": "vikhyat"
}
```
    
#### Error Response object 
Currently this is passed in the body, we need to change this to pass it in JSON format
 ```
404 Feature Flag not found 
 ```
</details>

### 3. 🔄 Update a feature flag
<details>

  #### API Endpoint
```
PATCH `/feature-flags/{flagId}`
```
#### Path param 
```
 <flagId> passing uuid of the feature flag
```
#### Request object

```
{
    "status": "DISABLED",
    "userId": "vikhyat187"
}
```
#### Sucess Response object
```
{
    "id": "22d400ca-8736-4c11-8a48-c74ff7d66f09",
    "name": "Test-flag-via-postman",
    "description": "Feature flag created via postman",
    "status": "DISABLED",
    "createdAt": 1744734096,
    "createdBy": "vikhyat",
    "updatedAt": 1745425567,
    "updatedBy": "vikhyat187"
}
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 4. 👤 Create user-specific override
<details>
  
#### API Endpoint
```
POST `/users/{userId}/feature-flags/{flagId}`
```
#### Path param 
```
<userId>  -> user for which feature flag has to be enabled
<flagId> -> feature flag which has to be enabled
```
#### Request object

```
{
    "status": "DISABLED",
    "userId": "vikhyat187" -> this is the user Id to store in the `createdBy` / `updatedBy` column
}
```
#### Sucess Response object
```
{
    "userId": "vikhyat",
    "flagId": "22d400ca-8736-4c11-8a48-c74ff7d66f09",
    "status": "DISABLED",
    "createdAt": 1745425825,
    "createdBy": "vikhyat187",
    "updatedAt": 1745425825,
    "updatedBy": "vikhyat187"
}
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 5. 🔍 Fetch User-Specific Feature Flag Details
<details>

  #### API Endpoint
```
GET `/users/{userId}/feature-flags/{flagId}`
```
#### Path param 
```
<userId>  -> user for which feature flag has to be enabled
<flagId> -> feature flag which has to be enabled
```
#### Request object

```
Empty
```
#### Sucess Response object
```
{
    "userId": "1234",
    "flagId": "22d400ca-8736-4c11-8a48-c74ff7d66f09",
    "status": "DISABLED",
    "createdAt": 1744735629,
    "createdBy": "vikhyat187",
    "updatedAt": 1745425794,
    "updatedBy": "vikhyat187"
}
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 6. 🔍 Fetch All Feature Flags for a User
<details>

  #### API Endpoint
```
GET `/users/{userId}/feature-flags/
```
#### Path param 
```
<userId>  -> user for which feature flag has to be enabled
```
#### Request object

```
Empty
```
#### Sucess Response object
```
[
    {
        "userId": "1234",
        "flagId": "22d400ca-8736-4c11-8a48-c74ff7d66f09",
        "status": "DISABLED",
        "createdAt": 1744735629,
        "createdBy": "vikhyat187",
        "updatedAt": 1745425794,
        "updatedBy": "vikhyat187"
    }
]
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 7. 🌐 Get All Feature Flags (Global)
<details>

  #### API Endpoint
```
GET `/feature-flags`
```

#### Request object

```
Empty
```
#### Sucess Response object
```
[
    {
        "id": "0cffec18-518a-41b2-b5e5-86604c06c38c",
        "name": "Test-flag-via-postman",
        "description": "Feature flag created via postman",
        "status": "ENABLED",
        "createdAt": 1745424103,
        "createdBy": "vikhyat",
        "updatedAt": 1745424103,
        "updatedBy": "vikhyat"
    },
    {
        "id": "22d400ca-8736-4c11-8a48-c74ff7d66f09",
        "name": "Test-flag-via-postman",
        "description": "Feature flag created via postman",
        "status": "DISABLED",
        "createdAt": 1744734096,
        "createdBy": "vikhyat",
        "updatedAt": 1745425567,
        "updatedBy": "vikhyat187"
    },
    {
        "id": "aaf474b1-0b0f-44d3-a648-82ac6754d7ba",
        "name": "Test-flag-via-postman",
        "description": "Feature flag created via postman",
        "status": "ENABLED",
        "createdAt": 1744733459,
        "createdBy": "vikhyat",
        "updatedAt": 1744733459,
        "updatedBy": "vikhyat"
    }
]
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 8. 🔄 Update Concurrency
<details>

  #### API Endpoint
```
POST `/reset-limit
```

#### Request object

```
{
    "pendingLimit": 20
}
```
#### Sucess Response object
```
Successfully updated concurrency limit
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```
</details>

### 9. ♻️ Reset Lambda Concurrency to Zero
<details>

  #### API Endpoint
```
PATCH `/mark-concurrency-zero`
```

#### Request object

```
Empty
```
#### Sucess Response object
```
Changed the reserved concurrency of the lambda function GetFeatureFlagFunction
```
    
#### Error Response object 
 ```
{
    "message": "Internal server error"
}
 ```

</details>


📎 Appendix
Glossary for beginners ([SSM](https://docs.aws.amazon.com/systems-manager/latest/userguide/documents.html), [IAM](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles.html), [Lambda](https://docs.aws.amazon.com/lambda/), [Dynamodb](https://docs.aws.amazon.com/dynamodb/), [Cloudwatch](https://docs.aws.amazon.com/cloudwatch/), [API gateway](https://docs.aws.amazon.com/apigateway/latest/developerguide/welcome.html).)



Instructions to use Feature flag service #152

Description

Feature Flag Service Documentation

📚 Introduction

⚙️ Architecture Overview

🛠️ Using the Feature Flag API

1. ➕ Create a feature flag

API Endpoint

Request object

Sucess Response object

Error Response object

2. 🔍 Get a feature flag

API Endpoint

Request object

Path param

Sucess Response object

Error Response object

3. 🔄 Update a feature flag

API Endpoint

Path param

Request object

Sucess Response object

Error Response object

4. 👤 Create user-specific override

API Endpoint

Path param

Request object

Sucess Response object

Error Response object

5. 🔍 Fetch User-Specific Feature Flag Details

API Endpoint

Path param

Request object

Sucess Response object

Error Response object

6. 🔍 Fetch All Feature Flags for a User

API Endpoint

Path param

Request object

Sucess Response object

Error Response object

7. 🌐 Get All Feature Flags (Global)

API Endpoint

Request object

Sucess Response object

Error Response object

8. 🔄 Update Concurrency

API Endpoint

Request object

Sucess Response object

Error Response object

9. ♻️ Reset Lambda Concurrency to Zero

API Endpoint

Request object

Sucess Response object

Error Response object

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