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API Limits & Best Practices

Trackly SMS does not impose API rate limits. The platform is built for high-volume sending and supports up to 50 million messages per minute across its infrastructure. Send as fast as your integration can push.

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Payload Limits

LimitValueResponse
Maximum request payload5 MB413 Payload Too Large
Individual contact payload4,000 bytes413 payload_too_large

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Batch Limits

Bulk endpoints accept up to 1,000 records per request. Each record is processed individually — partial success is possible.
OperationSingle EndpointBulk EndpointMax per Request
Send messagesPOST /v2/sendPOST /v2/send/bulk1,000
Create contactsPOST /v2/contactsPOST /v2/contacts/bulk1,000
Record revenuePOST /v2/revenuePOST /v2/revenue/bulk1,000
Import history—POST /v2/history/import1,000
To process more than 1,000 items, split your data into batches and send multiple requests.

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Best Practices

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Use Bulk Endpoints

Buffer messages locally and send in bulk batches. Sending 1,000 messages in a single bulk request is more efficient than 1,000 individual requests — fewer round trips, lower latency, and less overhead on both sides. 
import requests

# Send up to 1,000 messages in one request
messages = [
    {"to": f"+1415555{i:04d}", "body": "Flash sale! 50% off today."}
    for i in range(1000)
]

response = requests.post(
    "https://app.tracklysms.com/api/v2/send/bulk",
    headers={"X-Api-Key": "trk_your_api_key_here"},
    json={"list_number": "+18005551234", "messages": messages}
)

data = response.json()
print(f"Queued: {data['queued_count']}, Errors: {data['error_count']}")

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Handle Transient Errors

Use exponential backoff with jitter when you receive 5xx errors. These are transient and resolve on retry. 
import time
import random
import requests

def send_with_retry(url, headers, payload, max_retries=5):
    for attempt in range(max_retries):
        response = requests.post(url, headers=headers, json=payload)

        if response.status_code < 500:
            return response

        wait = (2 ** attempt) + random.uniform(0, 1)
        time.sleep(wait)

    raise Exception("Max retries exceeded")

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Handle Partial Failures

Bulk responses include per-record errors. Parse the errors array to identify and retry failed items without re-sending the entire batch. 
{
  "queued_count": 998,
  "error_count": 2,
  "errors": [
    {"index": 42, "to": "+1invalid", "code": "invalid_phone", "error": "Invalid recipient phone number format"},
    {"index": 501, "to": "+10000000000", "code": "not_sendable", "error": "VOIP numbers not allowed"}
  ]
}

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Parallelize Across Batches

Since there are no rate limits, you can send multiple bulk requests concurrently. Split large sends into 1,000-message batches and dispatch them in parallel for maximum throughput.

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Next Steps

Error Codes

Handle errors in your integration

Send Bulk

Send up to 1,000 messages per request