Optimizing API Requests for Large Lead Sets in Outbound Email Campaigns

Shayan H. · 2025-10-20 20:15:39.243942+00

Interesting question… I have a table where each row represents a lead. There’s an HTTP API column that pushes that lead to our email outbound platform. Problem is when we have 10,000 leads, we hit concurrent request rate limits on the email outbound’s API. Even after setting auto-retries and rate limiting on the HTTP API Column settings, many rows fail because of the email outbound’s API. Ideally we collapse the 10,000 leads into a few hundred requests, where each requests holds a few hundred leads. Is there a way to collapse many rows into one and still keep all the variables specific to each lead intact? Maybe it looks something like creating the JSON object as a plain text column for each row, then pasting each row of that column together somehow? Thanks!

Optimizing API Requests for Large Lead Sets in Outbound Email Campaigns | Clay

Clay Support
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To reduce outbound API rate limit issues, you can consolidate many leads into fewer HTTP API requests by batching them. This involves combining multiple lead rows into a single JSON array or object, so each request contains several leads with their variables intact.
Prepare a column that formats each lead as a JSON object.
Use a formula or automation to concatenate these JSON objects into a single array or payload, ensuring you stay within any cell or payload size limits.
Send this batched payload via the HTTP API column, adjusting your API endpoint and body to accept multiple leads per request.
This approach minimizes the number of requests and helps you stay within rate limits while preserving all lead-specific data. If your outbound platform supports bulk or batch endpoints, use those for optimal efficiency. [1] [2]
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Shayan H.
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Makes sense, but for the concatenation how do I set that up Is it like in another table and you have to “look up multiple rows” and concatenate? How do I set the number of rows I want to concatenate? Like every 100 rows should be batched together
Clay Support
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To batch every 100 lead rows together for grouped HTTP API requests in Clay, you can use the "write to table" feature:
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Use "write to table" to transfer your leads into a new table, grouping them as needed.
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In the destination table, use the "Merge Columns" feature or formulas to concatenate the JSON objects for each group of 100 leads.
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You can then use a lookup (like "Lookup Multiple Rows in Other Table") to pull and batch these grouped leads for your HTTP API requests, ensuring each batch preserves all lead-specific variables.
This approach allows you to control batch size and keep all variables intact for each lead in the grouped request [1] [2] [3].
Clay Support
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Was that helpful?
Clay Support
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If you need any more help setting up the concatenation or batching process, I’m here to assist. Would you like to provide more details about what you’re trying to achieve or any specific challenges you’re facing?
Andreas W.
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Talk to a person. This is interesting. Any chance there’s a Loom on this to see this in action?
Clay Support
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I understand your interest, and I’ll connect you to one of our human agents who can provide more detailed assistance. 😊
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Aditi S.
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Hi Shayan - thanks so much for reaching out and for your patience here.
Right now, Clay processes HTTP API calls at the row level, so there isn’t a built-in way to batch multiple rows into a single API request.
That said, there could be a workaround that’s similar to what you mentioned:
First, create a JSON payload column for each lead (e.g. {"email": {{email}}, "name": {{name}}})
Then assign a “batch ID” to group leads together (for example, every 100–200 rows)
In a secondary table, use "Lookup Multiple Rows" to pull all leads with the same batch ID - this gives you an array of JSON objects for that batch. You'd have to probably reformat that array properly for your API (might need a formula).
Finally, send one API request per batch instead of one per lead
I believe this could work for what you're hoping to do. Hopefully that helps!
Clay Support
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We haven't heard back from you here, so we're going to go ahead and close this thread out.
Still need help here? Reply back and someone will jump back in.
Have a question thats not related to this thread? We recommend kicking off a new ticket in the support channel!
Shayan H.
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Hey guys an update – I got the Batch ID -> look up multiple rows to work. Problem is that pasting all the JSON payloads together into one array exceeds the cell size limit! Also, it’s adding these backslashes This is the formula:
JSON.stringify(({{Lookup Multiple Rows in Other Table}}?.records||[])?.flat()?.map(r=>r?.["Contact JSON"])||[])
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Shayan H.
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Aditi S. any suggestions on what to do next?
Shayan H.
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Alternatively, if we have to do the row-by-row HTTP API call, any way to pace them out so we don’t hit rate limits? The minimum custom rate limit of 5 requests / second is too high
Aditi S.
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Hi Shayan - happy to hear that the logic is working.
Clay does has a cell size limit, and there’s no way to increase it at the moment. When you hit that limit, Clay starts escaping characters (those backslashes you’re seeing) and can’t store the full JSON array.
The best workaround is to reduce the batch size, so the payload stays within limits.
If you switch back to row-by-row requests, the lowest possible rate limit is 5 requests/sec, and that can’t be lowered right now, so pacing would need to be done manually (e.g. running smaller chunks at a time). For now, the best approach is to reduce batch size just enough to fit within Clay’s cell limits - that usually gets you the best balance of stability and efficiency.

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