OnDB uses an append-only storage model. Data is never overwritten or physically removed — every change is recorded as a new entry. Optional immutability via a Data Availability layer is available for use cases requiring on-chain verification.
How It Works Operation Behavior Create Appends a new record with a unique ID and timestamp Read Returns the latest version of a record by default (based on timestamp) Update Appends a NEW record with the same ID but a newer timestamp. The original record remains unchanged. Delete Appends a record with deleted: true (soft delete). Previous versions are preserved.
Traditional DB vs OnDB Aspect Traditional DB OnDB Update Modifies existing row in place Appends new version, old version preserved Delete Removes row from storage Soft delete, data is preserved History Lost unless manually tracked Automatic, all versions preserved Audit trail Requires additional implementation Built-in, cryptographically verified Storage Fixed per record Grows with each version
Benefits
Complete audit trail — All historical versions are preserved and can be queriedTamper-proof history — Past states cannot be altered or deletedCryptographic verifiability — When on-chain mode is enabled, every change is recorded with a block height and transaction hashConflict-free — No race conditions on writes since each version is a distinct record
Implications
Storage grows with each update (each version is a new record)
Historical versions can be queried by timestamp if needed
Data is never physically removed from the blockchain
“Deletes” are logical — they mark records as deleted but prior versions persist
Data Retention While the underlying storage is immutable, OnDB supports configurable retention policies per collection to manage storage costs.
Setting Description Cost Permanent Data stored indefinitely, no automatic cleanup Standard storage fees 30 days or less Free tier — no additional retention costs Free 31+ days Extended retention with monthly cost per KB Variable
The first 30 days of retention are free for all collections. Costs only apply for retention periods beyond 30 days.
Configuring Retention From the Dashboard :
Navigate to your application
Select the Retention tab
Expand a collection to view/edit its settings
Enter the retention period in days (leave empty for permanent)
Click Save to apply changes
Recommended Retention by Data Type Data Type Recommended Retention Session data 7-14 days User activity logs 30-90 days Analytics events 30-180 days Transaction records Permanent User profiles Permanent Audit logs Permanent or compliance-required period
Once data is cleaned up by the retention policy, it cannot be recovered. Ensure you have appropriate backups for critical data before setting retention limits.
Next Steps
CRUD Operations See how append-only storage affects CRUD operations
Data Storage Store data with payment handling
