Recommendation
Use Zapier to intake the nightly CSV into a Google Sheet (or S3), split rows into fixed-size batches, then call ChatGPT in batch mode (one prompt that returns a JSON array) with a Zapier Webhooks/OpenAI step. Use Zapier’s Delay and retries to throttle and exponential backoff to avoid API rate limits. Log outputs back to the sheet/CRM and alert on failures.

Why this works
Making one well-formed prompt that contains N leads and asks ChatGPT to return a JSON array reduces the number of API calls (fewer requests, more tokens per request). Zapier’s scheduling, parsing, and delay actions let you control concurrency without building a custom queue service.

Decision criteria (pick values by budget / scale / skill)
- Batch size: choose 5–50 leads per API call. Smaller if you need finer-grained results or you use a low token-limit model; larger if cost is a priority and you can tolerate longer prompts and marginally higher latency. Test to find the sweet spot.
- Model & token limits: if you need long company profiles, use smaller batches. If you have budget for GPT-4 with larger context, you can batch more.
- Throughput vs cost: batching reduces requests (lower throttling risk) but increases token cost per call. If you process tens of thousands of leads nightly, a code-based queue (Lambda/worker) may be cheaper and more robust.
- Team skills: Zapier = faster to implement (no-code). Custom worker = more control and better for very large scale.

Practical checklist (Zapier-focused)
1. Nightly trigger: Schedule by Zapier or watch folder in Google Drive.
2. Parse CSV: push rows into Google Sheets or use Formatter to convert CSV to line items.
3. Chunk rows: create a loop/logic to group N rows into one batch (use Zapier’s Line-Item utilities or create helper rows in Sheets).
4. Build prompt template: include instructions + an input array of rows. Request a strict JSON array output. Example skeleton:
- System: Describe format and that output must be valid JSON.
- User: "Given these leads, return [{id, company_profile, intent_reason, confidence}] for each input. Keep company_profile to 2–3 sentences, intent_reason 1 sentence. Respond only with JSON."
5. Call ChatGPT: use Zapier’s Webhooks to call OpenAI (or Zapier’s OpenAI app). Send one request per batch.
6. Parse response: use Formatter > Utilities to parse JSON and write results back to the sheet/CRM.
7. Throttle & retries: add Delay by Zapier between API calls (start with 500–2000 ms), and implement retry with exponential backoff on 429/5xx responses. Log failures to a dedicated sheet and notify Slack/email.
8. Monitoring: store request IDs, prompt sizes, and token estimates; set alerts when error rate or latency rises.

Prompt example (one-line idea to paste and adapt)
"Return a JSON array with an entry for each input lead (id, company_profile, intent_reason, confidence 0–1). company_profile: 2–3 concise sentences about the company. intent_reason: one sentence why they might buy. Only output valid JSON. Inputs: [ {id:1, name:..., domain:..., notes:...}, ... ]"

Best-for / Avoid-if
- Best for: teams wanting quick no-code deployment, moderate nightly volumes (hundreds–low thousands), and predictable CSV formats.
- Avoid if: you have very large dumps (tens of thousands) or need sub-second per-lead latency — build a dedicated queue/worker or use Make/clustered workers.

Final notes
Start conservative: batch size 10, delay 1s between requests, then ramp up while monitoring error/429 rates. If you want, I can sketch the exact Zap steps and a copy-paste prompt tailored to your CSV columns.

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