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docs: added a user guide for db migration
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‎docs/db_migration_guide.md‎

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# `LND Database Upgrade Guide`: A Two-Stage Migration for Node Operators
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*Table of Contents*
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- [Overview](#overview)
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- [Operation Modes](#operation-modes)
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- [Stage 1: Migration from bbolt to SQLite/Postgres (kvdb)](#stage-1-migration-from-bbolt-to-sqlitepostgres-kvdb)
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- [Choosing Your Target Backend](#choosing-your-target-backend)
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- [Postgres kvdb Migration](#postgres-kvdb-migration)
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- [SQLite kvdb Migration](#sqlite-kvdb-migration)
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- [Stage 2: Migration from kvdb to Relational Database](#stage-2-migration-from-kvdb-to-relational-database)
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- [Subsystem Readiness](#subsystem-readiness)
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- [Known Limitations and Edge Cases](#known-limitations-and-edge-cases)
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- [Best Practices for Node Operators](#best-practices-for-node-operators)
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- [Choosing the Right Path](#choosing-the-right-path)
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- [Timing Your Migration](#timing-your-migration)
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- [Validation](#validation)
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- [Implementation Examples](#implementation-examples)
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- [Migrating to SQLite kvdb](#migrating-to-sqlite-kvdb)
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- [Migrating Invoices to Relational Backend](#migrating-invoices-to-relational-backend)
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- [Future Improvements](#future-improvements)
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- [Conclusion](#conclusion)
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---
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## Overview
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The `LND Database Upgrade` process enables node operators to migrate from the legacy **bbolt** key-value store to modern **SQLite** or **PostgreSQL** backends—first in **kvdb mode**, then ultimately to a **relational database** format. This two-stage migration addresses long-standing performance bottlenecks, and lays the foundation for scalable, maintainable node operations.
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This guide explains the migration path, backend trade-offs, subsystem readiness, and best practices for safely upgrading your LND database.
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---
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## Operation Modes
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The LND database upgrade operates in two sequential stages, each with distinct tooling and implications:
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```mermaid
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flowchart TD
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%% 1. Define all nodes
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Bbolt["Bbolt (kvdb)"]
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SQLite["SQLite (kvdb)"]
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Postgres["Postgres (kvdb)"]
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M1_Sqlite["Migration #1 (lnd v0.19)<br>Invoices"]
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M2_Sqlite["Migration #2 (lnd v0.20)<br>Graph"]
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M3_Sqlite["Migration #3 (lnd v0.21)<br>Payments"]
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M1_Postgres["Migration #1 (lnd v0.19)<br>Invoices"]
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M2_Postgres["Migration #2 (lnd v0.20)<br>Graph"]
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M3_Postgres["Migration #3 (lnd v0.21)<br>Payments"]
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%% 2. Define all links (within and between graphs)
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Bbolt --> SQLite
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Bbolt --> Postgres
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SQLite --> M1_Sqlite
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M1_Sqlite --> M2_Sqlite
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M2_Sqlite --> M3_Sqlite
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Postgres --> M1_Postgres
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M1_Postgres --> M2_Postgres
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M2_Postgres --> M3_Postgres
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%% 3. Group nodes into subgraphs
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subgraph "Step 1: Migration via lndinit"
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Bbolt
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SQLite
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Postgres
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end
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subgraph "Step 2: Migration within lnd"
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M1_Sqlite
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M2_Sqlite
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M3_Sqlite
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M1_Postgres
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M2_Postgres
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M3_Postgres
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end
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%% 4. Apply Styles
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%% Define classes with explicit dark text color (#333)
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classDef bboltNode fill:#e2e3e5,stroke:#383d41,color:#333
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classDef sqliteNode fill:#d4edda,stroke:#155724,color:#333
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classDef postgresNode fill:#cce5ff,stroke:#004085,color:#333
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%% Apply classes to nodes
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class Bbolt bboltNode
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class SQLite,M1_Sqlite,M2_Sqlite,M3_Sqlite sqliteNode
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class Postgres,M1_Postgres,M2_Postgres,M3_Postgres postgresNode
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```
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- **Stage 1**: Migrate from bbolt to a SQL-based **kvdb** backend using the [lndinit](https://github.com/lightninglabs/lndinit/blob/main/docs/data-migration.md) tool.
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- **Stage 2**: Incrementally migrate subsystem data (invoices, graph, payments, etc.) from **kvdb** to SQL native **relational tables** as support becomes available.
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---
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## Stage 1: Migration from bbolt to SQLite/Postgres (kvdb)
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LND cannot run with mixed backends, so all users must first leave bbolt behind. This stage uses the `lndinit` utility to perform an offline migration.
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### Choosing Your Target Backend
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| Backend | Performance (in kvdb mode) | Default in LND? | Long-Term Viability |
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|-----------|--------------------------|------------------|----------------------|
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| Postgres | Mediocre | No | ✅ |
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| SQLite | Good | **Yes (future)** | ✅ |
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> 💡 **Recommendation**: Unless you require Postgres for infrastructure reasons,
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**migrate to SQLite kvdb** as your backend.
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### Postgres kvdb Migration
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A migration script is available via `lndinit`:
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- [Postgres migration script](https://github.com/lightninglabs/lndinit/blob/main/docs/data-migration.md#using-postgres-as-the-destination-remote-database)
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- **Caveat**: Users report degraded performance in kvdb mode. Only proceed if you plan to **immediately follow with Stage 2** to migrate the available data stores to relational DB.
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This will mitigate the poor Postgres performance on kvdb.
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### SQLite kvdb Migration
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- [SQLite migration script](https://github.com/lightninglabs/lndinit/blob/main/docs/data-migration.md#using-sqlite-as-the-destination-remote-database)
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- **Advantage**: Maintains good performance while waiting for full relational migration.
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---
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## Stage 2: Migration from kvdb to Relational Database
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This stage unlocks true SQL performance by restructuring data into relational tables. Migration is **per-subsystem** and **incremental**.
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### Subsystem Readiness
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| Subsystem | Relational Backend | Migration Script | Status |
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|---------------------|--------------------|------------------|--------|
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| Invoices | ✅ Available | ✅ | Available with **v0.19** |
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| Graph | ✅ Available | ✅ | Available with **v0.20** |
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| Payments | 🚧 In Progress | Planned | Targeted with **v0.21**|
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| Btcwallet | 🚧 In Progress | Planned | Targeted with **v0.21**|
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| Forwarding History | ❌ TBD | ❌ TBD | Future work |
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---
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## Known Limitations and Edge Cases
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- **Single database engine required**: LND requires a single consistent backend.
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You cannot run invoices in relational mode while graph remain in kvdb *unless*
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both are on the same SQL engine (e.g., SQLite).
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- **Data loss risk**: Always **back up your `data/` directory** before migration.
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- **Downtime required**: Stage 1 requires LND to be offline. Stage 2 is done at startup, requiring a LND restart.
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- **Postgres kvdb performance**: Postgres performance on kvdb is sub-optimal. It is
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recommended to make the stage 2 migration immediately to avoid performance bottlenecks. Certain RPCs like `listpayments` may not perform well on Postgres if the node has a lot of payments data. If your node operation is heavy
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on payments and `listpayments` performance is critical for you, we'd recommend
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not doing any migration and wait till version 0.21.0 is released.
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- **No migration path between SQL backend**: Once migrated to either Postgres or
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SQLite, it is not possible to switch to the other, so choose your target backend carefully.
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---
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## Best Practices for Node Operators
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### Choosing the Right Path
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- **For most users**: Choose SQLite, then migrate. Later, adopt relational backends subsystem-by-subsystem.
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- **Enterprise/Postgres users**: It is recommened to wait to start the migration
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until **payments relational backend** is ready, then perform **Stage 1 + Stage 2 in quick succession**.
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### Timing Your Migration
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- Perform migrations during **low-activity periods**.
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- Monitor LND release notes for relational DB support of different subsystems.
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### Validation
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1. Stop LND.
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2. Run migration with `lndinit`.
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3. Start LND with new backend flags, to execute stage 2 migrations.
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4. Validate node health: channels, balance, invoice/payment history.
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---
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## Implementation Examples
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### Migrating to SQLite kvdb
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```bash
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# Stop LND
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lnd --shutdown
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# Backup
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cp -r ~/.lnd ~/lnd-backup-$(date +%Y%m%d)
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# Run migration (e.g. sqlite)
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lndinit --debuglevel info migrate-db \
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--source.bolt.data-dir ~/.lnd/data \
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--dest.backend sqlite \
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--dest.sqlite.data-dir ~/.lnd/data --network mainnet
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# Start LND with SQLite backend
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lnd --db.backend=sqlite
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```
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> 📝 Add `db.backend=sqlite` to your `lnd.conf` to make it persistent.
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### Migrating Invoices to Relational Backend
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Once on LND v0.19+ with SQLite/Postgres:
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```bash
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# Ensure backend is set
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echo "db.backend=sqlite" >> ~/.lnd/lnd.conf
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# Start LND — invoice migration runs automatically
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lnd
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```
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Check logs for:
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```
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Migrating invoices from kvdb to relational format...
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Invoice migration completed successfully.
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```
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---
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## Future Improvements
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The LND team is actively working on:
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- **Payments relational backend** and migration tooling (Stage 2)
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- **Btcwallet relational backend** and migration tooling (Stage 2)
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- **Forwarding history** relational schema (long-term)
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- **Automatic detection** of migration readiness in `lnd`
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Node operators should monitor:
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- [LND GitHub Releases](https://github.com/lightningnetwork/lnd/releases)
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- [lndinit repository](https://github.com/lightninglabs/lndinit)
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---
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## Conclusion
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The LND database upgrade is a strategic two-stage process designed to eliminate bbolt performance limitations while ensuring data integrity and operational continuity.
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By **first migrating to SQLite/Postgres kvdb** and **then adopting relational backends incrementally**, node operators can achieve significant performance gains—especially for payment-heavy workloads—without rushing into unstable configurations.
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Choose your path wisely, back up rigorously, and stay informed. The future of LND is relational, and this guide ensures you get there safely.

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