How do you handle timestamp/versioning to detect stale data in the IndexedDB cache?

Question

ICSM Computer · Answer

To detect stale data in IndexedDB during synchronization with a remote server, the most common and reliable technique is to use
timestamps or versioning metadata on each record. Here’s how to handle it effectively:
1. Add a lastModified or version Field per Record
Every record stored in IndexedDB and on the server should include one of:
lastModified: A UTC timestamp (e.g., ISO 8601 or Unix Epoch).version: A monotonically increasing number (e.g., int or
UUID/ETag).
Example Record:
{
  id: "task_123",
  title: "Buy milk",
  completed: false,
  lastModified: "2025-07-11T04:32:12.000Z"  // ISO timestamp
}
2. Compare Timestamps during Sync
During sync:
Fetch latest server records (with their lastModified or version).Compare with the corresponding IndexedDB record.If the local version is older, update from the server.If the local version is newer, push to server.If both changed, trigger conflict resolution.
Example (timestamp comparison):
if (local.lastModified andlt; server.lastModified) {
    // Update local IndexedDB with server data
} else if (local.lastModified andgt; server.lastModified) {
    // Push local changes to server
} else {
    // Data is in sync – no action needed
}
3. Batch 
Versioning for Sync Tokens
If you want to track updates more efficiently:
Maintain a global lastSyncTimestamp.During sync, fetch records from the server with lastModified andgt; lastSyncTimestamp.Apply changes and update local IndexedDB.Then update lastSyncTimestamp.
4. Handle Clock Skew (if using timestamps)
Rely on server-generated timestamps whenever possible.On client-side creation, mark them as “pending” until server confirmation.
5. Optional: Use Hashing for Change Detection
For large documents:
Generate a hash (e.g., SHA-256) of the content.Store this alongside the record and compare it during sync.More accurate than timestamps alone.
Dexie.js Example
// Schema
db.tasks = new Dexie.Table("tasks", "++id, title, lastModified");
// Update with server data if newer
if (new Date(serverTask.lastModified) andgt; new Date(localTask.lastModified)) {
    await db.tasks.put(serverTask);
}
Summary
Field
Purpose
Format
lastModified
Detect stale updates
ISO Date or Unix Timestamp
version
Optional alternative to timestamps
Integer or UUID
syncStatus
Optional (e.g., pending, synced, conflict)
String

interview

How do you handle timestamp/versioning to detect stale data in the IndexedDB cache?

ICSM Computer

Can you answer this question?

1 Answers

1. Add a `lastModified` or `version` Field per Record

Example Record:

2. Compare Timestamps during Sync

Example (timestamp comparison):

3. Batch Versioning for Sync Tokens

4. Handle Clock Skew (if using timestamps)

5. Optional: Use Hashing for Change Detection

Dexie.js Example

Summary

Liked By

Field	Purpose	Format
`lastModified`	Detect stale updates	ISO Date or Unix Timestamp
`version`	Optional alternative to timestamps	Integer or UUID
`syncStatus`	Optional (e.g., `pending`, `synced`, `conflict`)	String