Handle two people editing the same record

Problem

One person can overwrite a change saved by someone else while both are editing the same record.

Before you start

Give each record a version, revision, or strong ETag. Require the client to send the version it originally loaded with every update.

Send the version with the edit

<form
  ng-put="/api/articles/42"
  on-success="article = $res; conflict = undefined"
  on-error="conflict = $res"
>
  <input name="version" type="hidden" value="{{ article.version }}" />
  <label>
    Title
    <input name="title" value="{{ article.title }}" required />
  </label>
  <button type="submit">Save article</button>
  <aside ng-if="conflict.current">
    <p>Someone saved a newer version: {{ conflict.current.title }}</p>
    <button
      type="button"
      ng-click="article = conflict.current; conflict = undefined"
    >
      Load newer version
    </button>
  </aside>
</form>

Server contract

Update only when the submitted version matches the stored version. Otherwise return 409 with a safe representation of the current record. Increment the version atomically with the successful update.

Failure path

Do not silently retry a conflicting write. Preserve the user’s draft while showing the current server value so they can compare or merge intentionally.

Apply it now

Add a version check to one record that is commonly edited by multiple people. Start with content, inventory, scheduling, or permission records.

Verify

Open the same record in two sessions. Save different values in both and confirm the second save receives 409 without overwriting the first.