fix: optimize SQLite connection pooling for single-writer architecture

Remove misleading max_connections config option and properly configure
SQLite connection pooling in the storage layer.

Changes:
- Set MaxOpenConns(1) for optimal SQLite performance
- Set MaxIdleConns(1) to keep connection alive
- Set ConnMaxLifetime(0) to never close connection
- Remove max_connections and max_lifetime from DatabaseConfig
- Update docs to clarify SQLite's single-writer architecture

Rationale:
SQLite is an embedded database with a single-writer lock. Multiple
connections cause lock contention and reduce performance. WAL mode
allows concurrent reads from the same connection, making connection
pooling unnecessary and counterproductive.

This change makes the configuration clearer and ensures optimal
SQLite performance by using a single long-lived connection.

1 files changed, 4 insertions, 12 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index 87ca4eb..91e79f7 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -31,9 +31,9 @@ type ServerConfig struct {
 
 // DatabaseConfig holds database configuration.
 type DatabaseConfig struct {
-        Path           string        `yaml:"path"`
-        MaxConnections int           `yaml:"max_connections"`
-        MaxLifetime    time.Duration `yaml:"max_lifetime"`
+        Path string `yaml:"path"`
+        // Note: SQLite connection pooling is handled internally in the storage layer.
+        // SQLite works best with a single connection due to its single-writer architecture.
 }
 
 // AuthConfig holds authentication configuration.
@@ -106,9 +106,7 @@ func Default() *Config {
                         WriteTimeout: 30 * time.Second,
                 },
                 Database: DatabaseConfig{
-                        Path:           "relay.db",
-                        MaxConnections: 10,
-                        MaxLifetime:    1 * time.Hour,
+                        Path: "relay.db",
                 },
                 Auth: AuthConfig{
                         Enabled:         false,
@@ -239,12 +237,6 @@ func applyEnvOverrides(cfg *Config) {
         if val := os.Getenv("MUXSTR_DATABASE_PATH"); val != "" {
                 cfg.Database.Path = val
         }
-        if val := os.Getenv("MUXSTR_DATABASE_MAX_CONNECTIONS"); val != "" {
-                var n int
-                if _, err := fmt.Sscanf(val, "%d", &n); err == nil {
-                        cfg.Database.MaxConnections = n
-                }
-        }
 
         // Auth
         if val := os.Getenv("MUXSTR_AUTH_ENABLED"); val != "" {