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Sometimes you need to know when an object you are syncing has been deleted in the external system. Detecting deletes is not a universal switch. It differs significantly between syncs that use checkpoints (fetching only changed data) and syncs that fetch all data on every run. Pick the strategy that matches your sync approach.

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Detecting deletes in syncs with checkpoints

When using checkpoints to only fetch changed data since the previous run, Nango has no built-in way to know which records disappeared on the provider side. You must actively tell Nango which IDs have been removed by calling nango.batchDelete() (full reference) inside the sync functions.

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When can you use this?

You can use nango.batchDelete() if the external API supports one of the following:
  • A dedicated “recently deleted” endpoint (e.g. GET /entities/deleted?since=...)
  • The ability to filter or sort by a deletion timestamp
  • The ability to filter or sort by last-modified timestamp and records include a flag like is_deleted, archived, etc.
If none of these are available, you cannot detect deletes with a checkpoint-based sync. You’ll either need to switch to a sync that fetches all data or skip deletion detection. Switching to fetching all data should not be done lightly. Make sure you understand the tradeoffs.

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Example sync with checkpoint and deletion detection

import { createSync } from 'nango';
import * as z from 'zod';

const AccountSchema = z.object({
  id: z.string(),
  name: z.string()
});

export default createSync({
  description: 'Sync Accounts with checkpoint & handle deletions',
  frequency: 'every 2 hours',
  endpoints: [{ method: 'GET', path: '/accounts', group: 'Accounts' }],
  models: { Account: AccountSchema },
  checkpoint: z.object({
    lastSyncedISO: z.string(),
  }),

  exec: async (nango) => {
    const checkpoint = await nango.getCheckpoint();
    const now = new Date().toISOString();

    // (1) Fetch newly created / updated accounts
    const res = await nango.get({
        endpoint: '/accounts',
        params: { ...(checkpoint && { since: checkpoint.lastSyncedISO }) }
    });
    await nango.batchSave(res.data, 'Account');

    // (2) Fetch deletions since the last run (if this is not the first run)
    if (checkpoint) {
        const deletedRes = await nango.get({
            endpoint: '/accounts/deleted',
            params: { since: checkpoint.lastSyncedISO }
        });

        // (3) Tell Nango which IDs have been deleted in the external system
        const toDelete = deletedRes.data.map((row: any) => ({ id: row.id }));
        if (toDelete.length) {
            await nango.batchDelete(toDelete, 'Account');
        }
    }

    // (4) Save checkpoint for next run
    await nango.saveCheckpoint({ lastSyncedISO: now });
  }
});

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Detecting deletes in syncs without checkpoints

Syncs that fetch all records on every run can automatically detect deletions. Nango detects removals by computing the diff between what existed before trackDeletesStart and what was saved between trackDeletesStart and trackDeletesEnd. (full reference).

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Example sync with deletion detection

import { createSync } from ‘nango’;
import * as z from ‘zod’;

const TicketSchema = z.object({
  id: z.string(),
  subject: z.string(),
  status: z.string()
});

export default createSync({
  description: ‘Fetch all help-desk tickets’,
  frequency: ‘every day’,
  endpoints: [{ method: ‘GET’, path: ‘/tickets’, group: ‘Tickets’ }],
  models: { Ticket: TicketSchema },

  exec: async (nango) => {
    // Mark the start of deletion tracking
    await nango.trackDeletesStart(‘Ticket’);

    const tickets = await nango.paginate<{ id: string; subject: string; status: string }>({
      endpoint: ‘/tickets’,
      paginate: { type: ‘cursor’, cursorPathInResponse: ‘next’, cursorNameInRequest: ‘cursor’, responsePath: ‘tickets’ }
    });

    for await (const page of tickets) {
      await nango.batchSave(page, ‘Ticket’);
    }

    // Detect and mark deleted records
    await nango.trackDeletesEnd(‘Ticket’);
  }
});

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How the algorithm works

  1. When trackDeletesStart is called, Nango marks the beginning of the deletion tracking window for the model.
  2. Records saved with batchSave between trackDeletesStart and trackDeletesEnd are tracked.
  3. When trackDeletesEnd is called, Nango compares what existed before trackDeletesStart with what was saved in the window.
  4. Any records missing from the new dataset are marked as deleted (soft delete). They remain accessible from the Nango cache, but with record._metadata.deleted === true.
Be careful with exception handling when using trackDeletesStart/trackDeletesEndNango only performs deletion detection (the “diff”) if a sync run completes successfully without any uncaught exceptions.Exception handling is critical:
  • If your sync doesn’t fetch the full dataset between the two calls (e.g. you catch and swallow an exception), Nango will attempt the diff on an incomplete dataset.
  • This leads to false positives, where valid records are mistakenly considered deleted.
What You Should DoIf a failure prevents full data retrieval, make sure the sync run fails and trackDeletesEnd is not being called:
  • Let exceptions bubble up and interrupt the run.
  • If you’re using try/catch, re-throw exceptions that indicate incomplete data.
How to use trackDeletesStart/trackDeletesEnd safelyIf some records are incorrectly marked as deleted, you can trigger a full resync (via the UI or API) to restore the correct data state.We strongly recommend not performing irreversible destructive actions (like hard-deleting records in your system) based solely on deletions reported by Nango. A full resync should always be able to recover from issues.

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Troubleshooting deletion detection issues

SymptomLikely cause
Records that still exist in the source API are shown as deleted in Nangosync didn’t save all records (silent failures) between trackDeletesStart and trackDeletesEnd
You never see deleted recordsCheck if deletion detection is implemented for the sync.
Questions, problems, feedback? Please reach out in the Slack community.