Every inventory sync tool connects to your channels through one of three methods, official APIs, in-store plugins, or feed files, and the method quietly decides what the tool can promise: how fast a sale propagates, what breaks when a channel hiccups, and whether you can audit any of it. Vendors rarely lead with their integration architecture, which is exactly why buyers should ask about it first.
The three methods
Official APIs. The platform’s own programmatic interface: the tool holds an authorized grant on your account and reads orders and writes quantities through it. For marketplaces, Amazon, eBay, Etsy, this is the only real method, and quality differences live in HOW the API is used: event-driven tools react to a sale notification in seconds, while polling tools ask on a timer, the interval that defines the oversell window. API connections also inherit the platform’s rate limits and auth lifecycles, mature tools handle throttling and token renewal invisibly; weak ones surface them as mystery sync failures.
Plugins. Code installed inside a store you host, WooCommerce or OpenCart, sitting at the source of events: a sale fires the plugin the moment it happens, no polling, no external round-trip to notice the change. For self-hosted stores this is the strongest signal available, and it is how our OpenCart and WooCommerce connections work, the plugin reports events instantly and receives quantity updates back. The trade: a plugin is software in your store, so it must be well-built (versioned, minimal surface, no core-file hacks) and kept current with platform releases.
Feed files. CSVs or XML posted on schedules, the oldest method, still common in supplier and dropship relationships and price-comparison channels. Feeds are batch by definition: fine for catalog data that changes daily, structurally wrong for stock truth on fast movers, a feed is always a photograph of a moving object.
Why the good answer is “both, by channel”
The methods map to what each channel offers: marketplaces expose APIs (event subscriptions where available), hosted platforms like Shopify expose APIs with webhooks, and self-hosted stores sync best with a plugin at the event source. A hub built this way, one pool, per-channel connections, uses the fastest honest method each channel supports, which is why “API versus plugin” is really a question about whether the vendor understood each channel deeply enough to connect it natively, the native-versus-generic difference buyers feel later as reliability.
The questions that expose a weak integration
- “When a sale happens on channel A, what triggers the update to channel B, an event or a timer?” Timers have intervals; intervals have oversell windows.
- “What happens when a push fails, retry, alert, or silence?” Failed pushes are inevitable (rate limits, expired tokens, platform outages); the difference between tools is whether failure is handled and visible or silent and cumulative.
- “Can I see the log?” Every push, timestamped, with its result, auditable sync is the difference between trusting a tool and hoping at it.
- “Is the connection yours or mine?” The grant should live on YOUR account, revocable by you, the ownership detail that matters at breakup time.
Then verify the answers yourself: the sync test takes an afternoon and outranks every architecture diagram.
Common questions
Are plugins less safe than APIs?
A well-built plugin is as safe as the store hosting it: proper versioning, no core modifications, minimal permissions. The risk is not the method; it is careless code, which afflicts API tools equally.
My supplier only offers a feed - am I stuck with batch?
For that supplier relationship, yes, so buffer for the feed’s staleness and treat feed-fed SKUs more conservatively than event-synced ones.
Do webhooks make polling obsolete?
Where platforms offer event subscriptions, event-driven wins outright; mature tools use events where they exist and tight, respectful polling only where they do not.
Does the method affect what I pay?
Indirectly and meaningfully: polling architectures cost vendors little and cost YOU the interval; event-driven engineering is the actual product, what sync tools charge for.
Connected the fastest honest way, per channel
APIs where platforms offer them, plugins at the source for self-hosted stores, one pool behind all of it, from $49/month with unlimited orders. See pricing.