'We sync with Sync Master, yet for some reason the numbers do not line up.' 'Before we knew it, Shopify inventory had gone back to an old value.' When we receive these questions, it is rarely a technical bug. Almost always the root cause is that 'the flow of information is not organized.' If you do not have a mental map of who writes which number where, and where it flows next, even a sync tool cannot do its real job.
In this article we share a simple way of thinking that helps you draw the flow of information between your sheet and Shopify as 'your own diagram.' Nothing complicated. Paper and a pen, or any drawing tool, is enough.
First decide 'where the source of truth lives'
When you draw the flow of information, the first thing to do is decide 'where the source of truth lives.' The source of truth is the home of the value that everyone agrees is correct—sometimes called the single source of truth. For inventory it means deciding, once and for all, 'whose number do we ultimately believe?'
The usual options are: (A) make the value in the Shopify admin the source of truth, (B) make the value in Google Sheets the source of truth, or (C) make the value in a warehouse app the source of truth. Each has pros and cons, but the important part is not 'which one you pick' but 'making a final choice.' If you configure tools without a single source of truth, numbers will collide somewhere, guaranteed.
Inputs and outputs of information
Once the source of truth is set, the next step is to organize 'where information comes from and where it goes.' If Google Sheets is your source of truth, information arrives in the sheet from many places—purchase plans, the results of a stocktake, real-stock reports from external warehouses, subtractions based on sales results, and so on.
And there are destinations as well. Shopify, slides for reporting, CSVs for accounting, summaries on the internal wiki. Listing every 'input' and 'output' as a bullet list makes you realize how much responsibility your sheet actually carries.
Start by listing them all
You may think 'we are not complex, listing is unnecessary.' But once you actually write them down, you will be surprised how many paths there are. Just for inputs you can easily reach five or six items: 'Amazon sales results,' 'Shopify's own sales results,' 'in-store POS,' 'monthly reports from external warehouses,' and more.
Doing this inventory of paths regularly surfaces improvement points like 'wait, no one uses this path anymore' or 'this path is manual but could be automated.' Before adopting a tool like Sync Master, draw a map of the current state first—it is surprisingly effective.
Is the sync one-way or two-way
The next thing to think about is 'one-way or two-way sync.' One-way means a structure like sheet → Shopify, where one side is the source of truth and the other is merely its destination. Two-way means both sides can be edited and changes are mirrored to each other.
To cut to the chase: for most stores, one-way is enough. In fact, two-way sync is hard to implement and operationally riskier. If the same SKU's stock is rewritten at the same time on the sheet and on Shopify, the question 'which value wins?' has no clean mechanical answer. Stay one-way and the rule 'the source of truth value is always correct' never wavers.
Sync Master is also built on the single-source-of-truth idea (there is only one source) and adopts a one-way design: write in Google Sheets → reflect in Shopify. This makes operations more stable and makes root cause analysis simpler when something goes wrong.
Pitfalls that appear once you draw the picture
With what we have covered, please try drawing it on paper. Put 'source of truth (e.g. Google Sheets)' in the center, place input arrows on the left and output arrows on the right. That simple diagram is enough. Once it is drawn, look at the arrows one by one.
- How often is this arrow updated
- Is the update manual or automated
- Who notices when the update fails
- Have there been any past incidents along this path
Once on paper, things like 'a path nobody really touches,' 'a path that depends entirely on one person,' or 'a path where no one notices when updates fail' become obvious. These are the things you want to tidy up before adopting Sync Master. Once you can draw the picture cleanly, the configuration of the sync tool tends to settle naturally.
Wrap-up: draw the map before reaching for the tool
When trying a new sync tool, it is tempting to start with 'feature comparison,' but what really matters is the step before that. Where is the source of truth for your store? Where does information come in and where does it go out? Is one-way enough, or do you really need two-way? Once these are sorted out, choosing a tool becomes remarkably simple.
Whether or not you choose Sync Master, draw the map on paper with a pen first. It is just ten minutes of work, but those ten minutes change your operational load six months later. In the next article, we will discuss the idea of using sync logs as an audit log.