> For the complete documentation index, see [llms.txt](https://docs.lingoql.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lingoql.com/sub0/apis-abi/practical-examples/wallet-backend-transactions-and-balances.md).

# Wallet backend: Transactions and balances

Use this page when the wallet starts moving real money.

### Best for

Balance updates, transaction history, and hot read endpoints.

### What it shows

* Action chaining inside one endpoint
* Extracting a prior result into a later write
* Endpoint-level caching for repeated reads

### Use this when

You want a production-shaped money flow without custom controller code.

### Pattern 1. Apply a fulfilled transaction to the user balance

This is the flagship wallet pattern on this page.

```json
{
  "id": "wallet-apply-transaction-01",
  "resource": "apply-fulfilled-transaction",
  "tokenize": {
    "type": "JWT",
    "algorithm": "HS256",
    "encryption_key": "$ENV.JWT_SECRET_KEY"
  },
  "protected": {
    "provide_as": "x-access-token",
    "extract_claims": ["id"]
  },
  "actionables": [
    {
      "id": 1,
      "mode": "QUERY",
      "no_op": true,
      "sql_query": {
        "query": "SELECT amount FROM transactions WHERE user_id = $1 AND status = 'FULFILLED' ORDER BY created_at DESC LIMIT 1",
        "parameters": ["$PROTECTED.id"]
      },
      "returnables": ["amount"]
    },
    {
      "id": 2,
      "mode": "QUERY",
      "depends_on": [
        {
          "resource_id": "self",
          "action_ids": [1],
          "extract_response_for": [
            {
              "extract": "amount",
              "for": "add_bal"
            }
          ]
        }
      ],
      "sql_query": {
        "query": "UPDATE users SET wallet_balance = wallet_balance + $1::float8, updated_at = $2::timestamptz WHERE id = $3 RETURNING wallet_balance AS user_wallet_balance",
        "parameters": ["add_bal", "$DATETIME", "$PROTECTED.id"]
      },
      "returnables": ["user_wallet_balance"],
      "main_returnable": true
    }
  ]
}
```

### Pattern 2. Cache recent transaction history

Use this when the same user opens the wallet screen often.

```json
{
  "id": "wallet-recent-transactions-01",
  "resource": "recent-transactions",
  "tokenize": {
    "type": "JWT",
    "algorithm": "HS256",
    "encryption_key": "$ENV.JWT_SECRET_KEY"
  },
  "protected": {
    "provide_as": "x-access-token",
    "extract_claims": ["id"]
  },
  "cacheable": {
    "read_from_cache": true,
    "cache_key": "recent_transactions_$PROTECTED.id",
    "duration": 60
  },
  "actionables": [
    {
      "id": 1,
      "mode": "QUERY",
      "sql_query": {
        "query": "SELECT id, amount, status, created_at::text FROM transactions WHERE user_id = $1 AND deleted_at IS NULL ORDER BY created_at DESC LIMIT 20",
        "parameters": ["$PROTECTED.id"]
      },
      "returnables": ["id", "amount", "status", "created_at"]
    }
  ]
}
```

<details>

<summary>MongoDB variant for the balance update</summary>

```json
{
  "id": "wallet-apply-transaction-mongo-01",
  "resource": "apply-fulfilled-transaction",
  "tokenize": {
    "type": "JWT",
    "algorithm": "HS256",
    "encryption_key": "$ENV.JWT_SECRET_KEY"
  },
  "protected": {
    "provide_as": "x-access-token",
    "extract_claims": ["id"]
  },
  "actionables": [
    {
      "id": 1,
      "mode": "QUERY",
      "no_op": true,
      "mongo_query": {
        "collection": "transactions",
        "action": "FETCH",
        "filter_predicate": {
          "user_id": "$PROTECTED.id",
          "status": "FULFILLED"
        }
      },
      "returnables": ["amount"]
    },
    {
      "id": 2,
      "mode": "QUERY",
      "depends_on": [
        {
          "resource_id": "self",
          "action_ids": [1],
          "extract_response_for": [
            {
              "extract": "amount",
              "for": "wallet_balance"
            }
          ]
        }
      ],
      "mongo_query": {
        "collection": "users",
        "action": "UPDATE",
        "filter_predicate": {
          "_id": "$PROTECTED.id"
        },
        "update_predicate": {
          "$inc": {
            "wallet_balance": "$PAYLOAD.wallet_balance"
          }
        },
        "with_timestamp": true
      },
      "returnables": ["wallet_balance"],
      "main_returnable": true
    }
  ]
}
```

</details>

When you need more execution detail, use [Action Chaining](/sub0/apis-abi/action-chaining.md) and [Caching](/sub0/apis-abi/caching.md).


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