nick-doc/08 - Operations/Database Operations.md

---
title: Database Operations
tags: [operations]
---

# Database Operations

Day-to-day operations for the two stateful services: **MongoDB 8.2** (primary data store) and **Redis 8** (cache, rate-limit counters, ephemeral session data).

For schema details see [[Data Models]]. For backup procedures and disaster recovery see [[Backup & Recovery]].

---

## 1. MongoDB

### 1.1 Connection

| Env | URI in compose | Auth |
|-----|---------------|------|
| Dev | `mongodb://mongodb:27017` | none |
| Prod | `mongodb://mongodb:27017` (private network) or with creds via `.env` | typically none on the private network, but enable `--auth` if exposed |

The DB name comes from `DB_NAME` (e.g. `marketplace`). See [[Environment Variables#database]].

Connect from a shell inside the host:

```bash
# Dev
docker exec -it nickdev-mongodb mongosh

# Prod
docker exec -it nickapp-mongodb mongosh
> use marketplace
> show collections
```

If auth is enabled:

```bash
docker exec -it nickapp-mongodb mongosh \
  -u "$MONGO_INITDB_ROOT_USERNAME" -p "$MONGO_INITDB_ROOT_PASSWORD" \
  --authenticationDatabase admin
```

### 1.2 Init scripts (`mongo-init/`)

The production compose bind-mounts `./mongo-init` into `/docker-entrypoint-initdb.d`. Mongo runs `*.js` and `*.sh` from this folder **only on a fresh datadir** (first boot of a new volume). Use this to:

- Create application users (`db.createUser({...})`)
- Bootstrap collections + indexes that must exist before the app starts

Example `mongo-init/01-create-user.js`:

```js
db = db.getSiblingDB('marketplace');
db.createUser({
  user: 'marketplace_app',
  pwd: process.env.MARKETPLACE_APP_PWD,
  roles: [{ role: 'readWrite', db: 'marketplace' }],
});
```

> [!warning] These scripts do **not** run when you restart an existing container. To force re-init, drop the `mongodb_data` volume — which destroys all data. Plan accordingly.

### 1.3 Indexes

Indexes are declared in Mongoose schemas under `backend/src/models/`. The app calls `Model.createIndexes()` on connection (via the model's `syncIndexes`/`ensureIndexes` lifecycle). Highlights:

| Collection | Key indexes |
|------------|-------------|
| `users` | `email` (unique), `googleId` (sparse), `role`, `createdAt` |
| `addresses` | `userId` + compound for primary lookup |
| `purchaserequests` | `buyerId`, `status`, `createdAt`, text index on `title`+`description` |
| `selleroffers` | `requestId`, `sellerId`, `status` |
| `payments` | `providerPaymentId` (unique sparse), `userId`, `status`, `createdAt`, `transactionHash` |
| `chats` | `participants` (array), `updatedAt` |
| `notifications` | `userId` + `read`, `createdAt` |
| `tempverifications` | TTL on `expiresAt` (auto-deletes expired OTPs) |

To verify a specific collection:

```js
db.payments.getIndexes()
```

To add a new index without code-gen — preferred path is to declare it in the Mongoose schema and ship a deploy. For emergency hotfixes:

```js
db.payments.createIndex({ providerPaymentId: 1 }, { unique: true, sparse: true });
```

### 1.4 TTL indexes

Currently used on `tempverifications.expiresAt` (5-minute auto-purge of email OTPs / passkey challenges). Mongo's TTL monitor runs every 60 seconds — purge isn't immediate.

If you add more TTL indexes:

```js
db.notifications.createIndex({ createdAt: 1 }, { expireAfterSeconds: 60 * 60 * 24 * 90 });  // 90 days
```

### 1.5 Backup with `mongodump`

```bash
# Connect into the container, dump locally, copy out
docker exec nickapp-mongodb sh -c \
  "mongodump --db=marketplace --archive=/tmp/marketplace-$(date +%F).archive --gzip"
docker cp nickapp-mongodb:/tmp/marketplace-$(date +%F).archive ./backups/

# Or stream directly to host
docker exec nickapp-mongodb \
  mongodump --db=marketplace --archive --gzip \
  > ./backups/marketplace-$(date +%F).gz
```

For full details (retention, RTO/RPO, offsite copies) see [[Backup & Recovery]].

### 1.6 Restore

```bash
# Restore an archive to an empty database
docker exec -i nickapp-mongodb \
  mongorestore --archive --gzip --drop \
  < ./backups/marketplace-2026-05-20.gz
```

`--drop` drops each collection before restoring. Omit it to merge.

> [!warning] Restoring is **destructive** to current data. Always practise on a staging clone first.

### 1.7 Migrations

There is no formal migration framework. Two patterns are used:

- **Mongoose schema changes** are forward-compatible (new optional fields default to `undefined`). Older documents will still load.
- **Data backfills** are one-shot scripts in `backend/src/scripts/` (e.g. `migrateUserPoints.ts`, `fix-transaction-hashes.js`, `fix-dispute-sellers.js`).

Pattern for a new migration:

1. Add a `src/seeds/migrate<Thing>.ts` script that is idempotent (use `$exists: false` guards).
2. Run on staging, confirm.
3. Take a backup ([[Backup & Recovery]]).
4. Run in production: `docker exec -it nickapp-backend node dist/seeds/migrate<Thing>.js`.
5. Commit the script (it serves as a record of what changed).

### 1.8 Common admin queries

```js
// Count by collection
db.users.countDocuments({ role: 'buyer' })

// Disk usage per collection
db.runCommand({ collStats: 'payments', scale: 1024*1024 }).size

// Slow queries
db.setProfilingLevel(1, { slowms: 200 })   // log queries > 200ms
db.system.profile.find().sort({ ts: -1 }).limit(10)

// Lock contention
db.serverStatus().locks
```

### 1.9 Seeding production safely

Seed scripts are designed to be idempotent for **categories** but **destructive** for users/addresses. Don't run `seed:all` in production.

Safe in production:

```bash
docker exec -it nickapp-backend node dist/seeds/seedCategories.js
docker exec -it nickapp-backend node dist/seeds/seedLevels.js
```

Optional auto-seed on startup: set `AUTO_SEED_ON_START=true` in `.env`. The bootstrap code only seeds when no non-admin users exist — safe to leave on.

> [!warning] **Never** run `seed:all` or `seed:users` against production. They drop the existing `users` and `addresses` collections.

---

## 2. Redis

### 2.1 Connection

Dev: `redis://redis:6379` (no password).
Prod: `redis://:<REDIS_PASSWORD>@redis:6379`. The compose command line is `redis-server --requirepass "$REDIS_PASSWORD"`.

Inspect:

```bash
docker exec -it nickapp-redis redis-cli -a "$REDIS_PASSWORD"
> INFO server
> DBSIZE
> KEYS *           # prod-unsafe on large datasets, use SCAN
```

### 2.2 What we store

- **Rate-limit counters** for `express-rate-limit`
- **Session data** for refresh-token tracking and revocation lists
- **Socket.IO adapter state** (when scaled horizontally — currently single-node)
- **Application caches** (TTL'd keys for expensive aggregates)
- **Idempotency keys** for webhook deduplication

Key prefixes follow `<service>:<entity>:<id>`. E.g. `payment:idem:<requestId>`, `auth:refresh:<userId>`.

### 2.3 Persistence

Redis 8 defaults to **RDB snapshots** + optional **AOF**. Our compose uses the default config:

- RDB snapshot triggers: `save 3600 1`, `save 300 100`, `save 60 10000`.
- AOF is **disabled** by default.
- RDB file lives at `/data/dump.rdb` inside the `redis_data` volume.

**To enable AOF** for stronger durability, override the command in `docker-compose.production.yml`:

```yaml
redis:
  command: ["sh","-lc","redis-server --requirepass \"$${REDIS_PASSWORD}\" --appendonly yes --appendfsync everysec"]
```

`appendfsync everysec` is the common compromise: at most 1 second of writes lost on crash, with negligible perf impact.

### 2.4 Eviction policy

Default is `noeviction` — Redis refuses writes when memory is full. For our use (caches that can be regenerated), set:

```bash
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" \
  CONFIG SET maxmemory 256mb
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" \
  CONFIG SET maxmemory-policy allkeys-lru
```

Persist by adding to a custom `redis.conf` mounted at `/usr/local/etc/redis/redis.conf` (then change the compose `command:` to `["redis-server","/usr/local/etc/redis/redis.conf","--requirepass",...]`).

### 2.5 Backup

Redis backups are usually unnecessary (the data is regeneratable) but still cheap:

```bash
# Snapshot now
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" BGSAVE
docker cp nickapp-redis:/data/dump.rdb ./backups/redis-$(date +%F).rdb
```

`BGSAVE` is non-blocking (forks). For AOF, copy `/data/appendonly.aof` too.

### 2.6 Cache flush

When deploying breaking changes to cached schemas:

```bash
# Flush everything (DEV ONLY)
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" FLUSHALL

# Targeted (safer)
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" \
  --scan --pattern 'payment:idem:*' | \
  xargs -L 1 docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" DEL
```

> [!warning] `FLUSHALL` will sign out every user with an active refresh token and reset every rate-limit counter. Avoid in production unless that is what you want.

### 2.7 Monitoring

```bash
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" INFO stats
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" INFO memory
docker exec nickapp-redis redis-cli -a "$REDIS_PASSWORD" SLOWLOG GET 10
```

Watch `evicted_keys`, `keyspace_misses`, `rejected_connections` — see [[Monitoring]] for thresholds.

---

## 3. Maintenance windows

For both DBs, schedule a window when:

- Bumping major version (Mongo 8 → 9, Redis 8 → 9)
- Restoring from backup
- Running a destructive migration

Suggested checklist:

1. Announce in #ops Slack / status page.
2. Trigger `mongodump` (see [[Backup & Recovery]]).
3. Stop the backend container so writes stop: `docker compose stop nickapp-backend`.
4. Perform the operation.
5. Restart backend: `docker compose start nickapp-backend`.
6. Verify health: `curl https://amn.gg/api/health`.
7. Close window.

---

## 4. Cross-links

- [[Backup & Recovery]] — formal backup/restore procedures, RTO/RPO targets, offsite storage.
- [[Monitoring]] — what metrics to watch (slow queries, evictions, replication lag).
- [[Incident Response]] — runbooks for "MongoDB unreachable" and "Redis unreachable".
- [[Data Models]] — schema details for every collection.