## Backend Support

HeroDB supports two storage backends, both with full encryption support:

- **redb** (default): Full-featured, optimized for production use
- **sled**: Alternative embedded database with encryption support

### Starting HeroDB with Different Backends

```bash
# Use default redb backend
./target/release/herodb --dir /tmp/herodb_redb --port 6379

# Use sled backend
./target/release/herodb --dir /tmp/herodb_sled --port 6379 --sled

# Use redb with encryption
./target/release/herodb --dir /tmp/herodb_encrypted --port 6379 --encrypt --key mysecretkey

# Use sled with encryption
./target/release/herodb --dir /tmp/herodb_sled_encrypted --port 6379 --sled --encrypt --key mysecretkey
```

### Command Support by Backend

Command Category | redb | sled | Notes |
|-----------------|------|------|-------|
**Strings** | | | |
SET | ✅ | ✅ | Full support |
GET | ✅ | ✅ | Full support |
DEL | ✅ | ✅ | Full support |
EXISTS | ✅ | ✅ | Full support |
INCR/DECR | ✅ | ✅ | Full support |
MGET/MSET | ✅ | ✅ | Full support |
**Hashes** | | | |
HSET | ✅ | ✅ | Full support |
HGET | ✅ | ✅ | Full support |
HGETALL | ✅ | ✅ | Full support |
HDEL | ✅ | ✅ | Full support |
HEXISTS | ✅ | ✅ | Full support |
HKEYS | ✅ | ✅ | Full support |
HVALS | ✅ | ✅ | Full support |
HLEN | ✅ | ✅ | Full support |
HMGET | ✅ | ✅ | Full support |
HSETNX | ✅ | ✅ | Full support |
HINCRBY/HINCRBYFLOAT | ✅ | ✅ | Full support |
HSCAN | ✅ | ✅ | Full support with pattern matching |
**Lists** | | | |
LPUSH/RPUSH | ✅ | ✅ | Full support |
LPOP/RPOP | ✅ | ✅ | Full support |
LLEN | ✅ | ✅ | Full support |
LRANGE | ✅ | ✅ | Full support |
LINDEX | ✅ | ✅ | Full support |
LTRIM | ✅ | ✅ | Full support |
LREM | ✅ | ✅ | Full support |
BLPOP/BRPOP | ✅ | ❌ | Blocking operations not in sled |
**Expiration** | | | |
EXPIRE | ✅ | ✅ | Full support in both |
TTL | ✅ | ✅ | Full support in both |
PERSIST | ✅ | ✅ | Full support in both |
SETEX/PSETEX | ✅ | ✅ | Full support in both |
EXPIREAT/PEXPIREAT | ✅ | ✅ | Full support in both |
**Scanning** | | | |
KEYS | ✅ | ✅ | Full support with patterns |
SCAN | ✅ | ✅ | Full cursor-based iteration |
HSCAN | ✅ | ✅ | Full cursor-based iteration |
**Transactions** | | | |
MULTI/EXEC/DISCARD | ✅ | ❌ | Only supported in redb |
**Encryption** | | | |
Data-at-rest encryption | ✅ | ✅ | Both support [age](age.tech) encryption |
AGE commands | ✅ | ✅ | Both support AGE crypto commands |
**Full-Text Search** | | | |
FT.CREATE | ✅ | ✅ | Create search index with schema |
FT.ADD | ✅ | ✅ | Add document to search index |
FT.SEARCH | ✅ | ✅ | Search documents with query |
FT.DEL | ✅ | ✅ | Delete document from index |
FT.INFO | ✅ | ✅ | Get index information |
FT.DROP | ✅ | ✅ | Drop search index |
FT.ALTER | ✅ | ✅ | Alter index schema |
FT.AGGREGATE | ✅ | ✅ | Aggregate search results |

### Performance Considerations

- **redb**: Optimized for concurrent access, better for high-throughput scenarios
- **sled**: Lock-free architecture, excellent for specific workloads

### Encryption Features

Both backends support:
- Transparent data-at-rest encryption using the `age` encryption library
- Per-database encryption (databases >= 10 are encrypted when `--encrypt` flag is used)
- Secure key derivation using the master key

### Backend Selection Examples

```bash
# Example: Testing both backends
redis-cli -p 6379 SET mykey "redb value"
redis-cli -p 6381 SET mykey "sled value"

# Example: Using encryption with both
./target/release/herodb --port 6379 --encrypt --key secret123
./target/release/herodb --port 6381 --sled --encrypt --key secret123

# Both support the same Redis commands
redis-cli -p 6379 HSET user:1 name "Alice" age "30"
redis-cli -p 6381 HSET user:1 name "Alice" age "30"

# Both support SCAN operations
redis-cli -p 6379 SCAN 0 MATCH user:* COUNT 10
redis-cli -p 6381 SCAN 0 MATCH user:* COUNT 10
```

### Migration Between Backends

To migrate data between backends, use Redis replication or dump/restore:

```bash
# Export from redb
redis-cli -p 6379 --rdb dump.rdb

# Import to sled
redis-cli -p 6381 --pipe < dump.rdb
```