Sending Salesforce Records as JSON in Batches with Queueable Apex

Introduction

In Salesforce projects, it’s common to integrate with external systems by sending large volumes of records via REST APIs. However, due to Salesforce governor limits (like heap size and callout limits), you cannot send all records in one go.

The solution? Queueable Apex with batch processing.

In this post, we’ll walk through a reusable Salesforce Apex class (JsonSender) that:

Splits records into smaller batches (default 200 per batch)
Converts records into JSON payloads
Sends them via HTTP callouts
Chains jobs automatically until all records are sent

Why Use Queueable Apex for Callouts?

Handles asynchronous processing
Supports chained execution (for multiple batches)
Allows callouts (unlike batch Apex finish)
Helps stay within governor limits

The JsonSender Class (Fixed Version)

Here’s the final, production-ready version of our JsonSender utility:

public class JsonSender implements Queueable, Database.AllowsCallouts {
    private List<SObject> records;
    private Integer startIndex;
    private String endpoint;
    private static final Integer BATCH_SIZE = 200;

    public JsonSender(List<SObject> records, String endpoint, Integer startIndex) {
        this.records = records;
        this.endpoint = endpoint;
        this.startIndex = startIndex != null ? startIndex : 0;
    }

    public void execute(QueueableContext context) {
        Integer endIndex = Math.min(startIndex + BATCH_SIZE, records.size());
        List<SObject> batch = new List<SObject>();
        for (Integer i = startIndex; i < endIndex; i++) {
            batch.add(records[i]);
        }

        sendBatch(batch);

        if (endIndex < records.size()) {
            Id jobId = System.enqueueJob(new JsonSender(records, endpoint, endIndex));
            System.debug('Chained Job ID: ' + jobId);
        }
    }

    private void sendBatch(List<SObject> batch) {
        String jsonPayload = JSON.serialize(new Map<String, Object>{
            'data' => batch,
            'count' => batch.size()
        });

        HttpRequest req = new HttpRequest();
        req.setEndpoint(endpoint);
        req.setMethod('POST');
        req.setHeader('Content-Type', 'application/json');
        req.setBody(jsonPayload);
        req.setTimeout(120000);

        Http http = new Http();

        try {
            HttpResponse res = http.send(req);
            if (res.getStatusCode() >= 400) {
                System.debug('Error sending data. Status: ' + res.getStatusCode() + 
                             ', Response: ' + res.getBody());
            } else {
                System.debug('✅ Sent ' + batch.size() + ' records successfully. Status: ' 
                             + res.getStatusCode());
            }
        } catch (Exception e) {
            System.debug('❌ Callout failed: ' + e.getMessage());
        }
    }

    // Helper method to start sending
    public static void send(List<SObject> records, String endpoint) {
        if (!records.isEmpty()) {
            System.enqueueJob(new JsonSender(records, endpoint, 0));
        }
    }
}

public class JsonSender implements Queueable, Database.AllowsCallouts {
    private List<SObject> records;
    private Integer startIndex;
    private String endpoint;
    private static final Integer BATCH_SIZE = 200;

    public JsonSender(List<SObject> records, String endpoint, Integer startIndex) {
        this.records = records;
        this.endpoint = endpoint;
        this.startIndex = startIndex != null ? startIndex : 0;
    }

    public void execute(QueueableContext context) {
        Integer endIndex = Math.min(startIndex + BATCH_SIZE, records.size());
        List<SObject> batch = new List<SObject>();
        for (Integer i = startIndex; i < endIndex; i++) {
            batch.add(records[i]);
        }

        sendBatch(batch);

        if (endIndex < records.size()) {
            Id jobId = System.enqueueJob(new JsonSender(records, endpoint, endIndex));
            System.debug('Chained Job ID: ' + jobId);
        }
    }

    private void sendBatch(List<SObject> batch) {
        String jsonPayload = JSON.serialize(new Map<String, Object>{
            'data' => batch,
            'count' => batch.size()
        });

        HttpRequest req = new HttpRequest();
        req.setEndpoint(endpoint);
        req.setMethod('POST');
        req.setHeader('Content-Type', 'application/json');
        req.setBody(jsonPayload);
        req.setTimeout(120000);

        Http http = new Http();

        try {
            HttpResponse res = http.send(req);
            if (res.getStatusCode() >= 400) {
                System.debug('Error sending data. Status: ' + res.getStatusCode() + 
                             ', Response: ' + res.getBody());
            } else {
                System.debug('✅ Sent ' + batch.size() + ' records successfully. Status: ' 
                             + res.getStatusCode());
            }
        } catch (Exception e) {
            System.debug('❌ Callout failed: ' + e.getMessage());
        }
    }

    // Helper method to start sending
    public static void send(List<SObject> records, String endpoint) {
        if (!records.isEmpty()) {
            System.enqueueJob(new JsonSender(records, endpoint, 0));
        }
    }
}

How It Works

Initialization
Call the class with: JsonSender.send(accountList, 'https://api.example.com/data');
Batching
Records are chunked into 200 per batch (configurable).
Serialization
Each batch is converted into JSON: { "data": [...records...], "count": 200 }
Callout
Data is sent via HTTP POST to the external endpoint.
Job Chaining
If more records remain, a new Queueable job is enqueued automatically.

✅ Benefits of This Approach

Works with any SObject list
Handles large record volumes safely
Provides robust error handling
Easy to extend (logging, retries, etc.)

🚀 Conclusion

By combining Queueable Apex + Callouts + JSON, we can build scalable and reliable Salesforce integrations.

This pattern ensures:

Bulk records are processed efficiently
Salesforce limits are respected
API calls are reliable with error handling

You can now adapt JsonSender for Accounts, Contacts, Opportunities, or any custom object that needs to be sent to an external system.