Shopify API Integration Checklist for Agencies
Most Shopify integrations that break in production weren't badly coded — they were scoped with an incomplete picture of the other system. This checklist covers the five areas worth confirming before an integration is quoted or built: access, rate limits, sync strategy, error handling, and testing with data that actually looks like the client's.
1. Credentials & Access
Before any code gets written, confirm access actually exists — this is the most common cause of a stalled integration kickoff.
- Shopify Admin API access scoped correctly (custom app or Shopify-approved public app, with only the access scopes the integration actually needs).
- Valid API credentials for the external system — API key, OAuth app, or equivalent — obtained from someone with authority to issue them, not a shared or soon-to-expire login.
- Confirmed API documentation for the external system, including which endpoints are actually usable at the client's account tier (some are gated behind higher-cost plans).
- A named technical contact on the external-system side who can answer questions once integration work is underway.
2. Rate Limits — Both Sides
Every integration has two rate limits to respect, not one — and the tighter of the two sets the real ceiling.
- Shopify's API rate limits understood for the API version in use (REST leaky-bucket limits or GraphQL query-cost limits), and factored into how the integration batches requests.
- The external system's rate limits confirmed directly with their documentation or support — don't assume it matches Shopify's.
- A plan for what happens when a rate limit is hit mid-sync (queuing and backoff, not a silent failure or a hard crash).
- Bulk operations (Shopify's Bulk Operations API) considered for any large one-time data pull, instead of paging through thousands of individual REST calls.
3. Real-Time vs. Batch Sync
This decision shapes the entire integration architecture — make it deliberately, not by default.
- A clear answer on whether the business actually needs real-time sync (webhooks) or whether scheduled batch sync is sufficient and simpler to maintain.
- Webhook endpoints registered, verified (HMAC signature validation), and monitored for delivery failures if real-time sync is used.
- A defined sync direction for every data type — Shopify to external system, external system to Shopify, or two-way — since two-way sync needs explicit conflict-resolution rules.
- A documented sync frequency for batch jobs, and what happens if a scheduled run is missed or overlaps with the next one.
4. Error Handling & Retry Logic
An integration that fails silently is worse than one that fails loudly — this is where most post-launch firefighting comes from.
- Retry logic with exponential backoff for transient failures (timeouts, temporary 5xx responses), rather than an immediate hard failure.
- A defined limit on retries, with failed events logged and surfaced somewhere a human will actually see them — not just written to a log file no one checks.
- Idempotency handled for anything that could be triggered twice (a webhook redelivery, a retried batch job) so it doesn't create duplicate orders, customers, or inventory adjustments.
- An alerting mechanism (email, Slack, or equivalent) for sustained failures, not just a dashboard someone has to remember to check.
5. Testing With Real Data
Sandbox testing catches the easy bugs. Real data catches the ones that actually break in production.
- The integration tested against a copy of the client's real product, customer, or order data — not just clean sandbox fixtures — since real data reliably surfaces edge cases (missing fields, unusual characters, legacy records) that sandbox data doesn't.
- Volume tested at something close to real scale before go-live, especially for a first full sync, to catch rate-limit and performance issues before the client hits them.
- A rollback or pause plan confirmed in case the integration needs to be turned off quickly after go-live without leaving data in a broken in-between state.
- A monitoring window planned for the first few days post-launch, with someone actually watching for failures rather than assuming a clean test run means it's done.
For the broader cost and timeline picture an integration fits into, see our guide on estimating a Shopify development project. If the requirement isn't clearly an integration versus a simpler theme-level fix, our theme vs. custom app guide covers that distinction.
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