diff --git a/crates/core/src/admin/table/mod.rs b/crates/core/src/admin/table/mod.rs
index 25a00dc8..4df367c3 100644
--- a/crates/core/src/admin/table/mod.rs
+++ b/crates/core/src/admin/table/mod.rs
@@ -40,6 +40,7 @@ fn get_conn_and_migration_path(
       Ok((
         trailbase_sqlite::Connection::new(
           move || {
+            // TODO: We should load WASM SQLite functions, since migrations may depend on them.
             return trailbase_extension::connect_sqlite(
               Some(db_path.clone()),
               Some(json_registry.clone()),
@@ -52,7 +53,7 @@ fn get_conn_and_migration_path(
       ))
     }
     _ => Ok((
-      state.conn().clone(),
+      (*state.connection_manager().main_entry().connection).clone(),
       (state.data_dir().migrations_path().join("main")),
     )),
   };
diff --git a/crates/core/src/app_state.rs b/crates/core/src/app_state.rs
index 26a49337..17914901 100644
--- a/crates/core/src/app_state.rs
+++ b/crates/core/src/app_state.rs
@@ -248,6 +248,7 @@ impl AppState {
     return &self.state.json_schema_registry;
   }
 
+  #[cfg(test)]
   pub fn conn(&self) -> &trailbase_sqlite::Connection {
     return &self.state.conn;
   }
@@ -260,7 +261,7 @@ impl AppState {
     return &self.state.logs_conn;
   }
 
-  pub(crate) fn connection_manager(&self) -> ConnectionManager {
+  pub fn connection_manager(&self) -> ConnectionManager {
     return self.state.connection_manager.clone();
   }
 
diff --git a/crates/core/src/auth/api/avatar.rs b/crates/core/src/auth/api/avatar.rs
index c45a9f37..5c84af4b 100644
--- a/crates/core/src/auth/api/avatar.rs
+++ b/crates/core/src/auth/api/avatar.rs
@@ -139,8 +139,8 @@ pub async fn delete_avatar_handler(
     static ref SQL: String = format!("DELETE FROM {AVATAR_TABLE} WHERE user = ?1");
   }
 
-  state
-    .conn()
+  let main_conn = state.connection_manager().main_entry().connection;
+  main_conn
     .execute(&*SQL, [rusqlite::types::Value::Blob(user.uuid.into())])
     .await?;
 
diff --git a/crates/core/src/connection.rs b/crates/core/src/connection.rs
index bc2a494f..a43928ed 100644
--- a/crates/core/src/connection.rs
+++ b/crates/core/src/connection.rs
@@ -55,7 +55,7 @@ struct ConnectionKey {
 }
 
 #[derive(Clone)]
-pub(crate) struct ConnectionEntry {
+pub struct ConnectionEntry {
   pub connection: Arc<Connection>,
   pub metadata: Arc<ConnectionMetadata>,
 }
@@ -157,7 +157,7 @@ impl ConnectionManager {
   //   return self.state.main.read().connection.clone();
   // }
 
-  pub(crate) fn main_entry(&self) -> ConnectionEntry {
+  pub fn main_entry(&self) -> ConnectionEntry {
     return self.state.main.read().clone();
   }
 
@@ -169,7 +169,7 @@ impl ConnectionManager {
   //   return Ok(self.get_entry(main, attached_databases)?.connection);
   // }
 
-  pub(crate) fn get_entry(
+  pub fn get_entry(
     &self,
     main: bool,
     attached_databases: Option<BTreeSet<String>>,
@@ -206,7 +206,7 @@ impl ConnectionManager {
     };
   }
 
-  pub(crate) fn get_entry_for_qn(
+  pub fn get_entry_for_qn(
     &self,
     name: &trailbase_schema::QualifiedName,
   ) -> Result<ConnectionEntry, ConnectionError> {
diff --git a/crates/core/src/records/transaction.rs b/crates/core/src/records/transaction.rs
index cfbebaf3..6a631290 100644
--- a/crates/core/src/records/transaction.rs
+++ b/crates/core/src/records/transaction.rs
@@ -1,6 +1,8 @@
 use axum::extract::{Json, State};
 use base64::prelude::*;
 use serde::{Deserialize, Serialize};
+use std::sync::Arc;
+use trailbase_schema::QualifiedName;
 use utoipa::ToSchema;
 
 use crate::app_state::AppState;
@@ -56,19 +58,47 @@ pub async fn record_transactions_handler(
   user: Option<User>,
   Json(request): Json<TransactionRequest>,
 ) -> Result<Json<TransactionResponse>, RecordError> {
+  // NOTE: We may want to make this user-configurable. The cost also heavily depends on whether
+  // `request.transaction == true`.
   if request.operations.len() > 128 {
     return Err(RecordError::BadRequest("Transactions exceed limit: 128"));
   }
 
+  if request.operations.is_empty() {
+    return Ok(Json(TransactionResponse { ids: vec![] }));
+  }
+
   type Op = dyn (FnOnce(&rusqlite::Connection) -> Result<Option<String>, RecordError>) + Send;
 
+  let mut db: (String, Option<Arc<trailbase_sqlite::Connection>>) = Default::default();
+  let mut get_api =
+    |state: &AppState, api_name: &str, idx: usize| -> Result<RecordApi, RecordError> {
+      let api = state
+        .lookup_record_api(api_name)
+        .ok_or_else(|| RecordError::ApiNotFound)?;
+      if !api.is_table() {
+        return Err(RecordError::ApiRequiresTable);
+      }
+
+      // Check that all ops reference same DB.
+      let db_name = get_db_name(api.qualified_name());
+      if idx == 0 {
+        db = (db_name.to_string(), Some(api.conn().clone()));
+      } else if db_name != db.0 {
+        return Err(RecordError::BadRequest("ops can only touch same db"));
+      }
+
+      return Ok(api);
+    };
+
   let operations: Vec<Box<Op>> = request
     .operations
     .into_iter()
-    .map(|op| -> Result<Box<Op>, RecordError> {
+    .enumerate()
+    .map(|(idx, op)| -> Result<Box<Op>, RecordError> {
       return match op {
         Operation::Create { api_name, value } => {
-          let api = get_api(&state, &api_name)?;
+          let api = get_api(&state, &api_name, idx)?;
           let mut record = extract_record(value)?;
 
           if api.insert_autofill_missing_user_id_columns()
@@ -121,7 +151,7 @@ pub async fn record_transactions_handler(
           record_id,
           value,
         } => {
-          let api = get_api(&state, &api_name)?;
+          let api = get_api(&state, &api_name, idx)?;
           let record = extract_record(value)?;
           let record_id = api.primary_key_to_value(record_id)?;
           let (_index, pk_column) = api.record_pk_column();
@@ -163,7 +193,7 @@ pub async fn record_transactions_handler(
           api_name,
           record_id,
         } => {
-          let api = get_api(&state, &api_name)?;
+          let api = get_api(&state, &api_name, idx)?;
           let record_id = api.primary_key_to_value(record_id)?;
 
           let acl_check = api.build_record_level_access_check(
@@ -190,9 +220,12 @@ pub async fn record_transactions_handler(
     })
     .collect::<Result<Vec<_>, _>>()?;
 
-  let ids = if request.transaction.unwrap_or(true) {
-    state
-      .conn()
+  let conn = db
+    .1
+    .ok_or_else(|| RecordError::Internal("missing db".into()))?;
+
+  let ids = if request.transaction.unwrap_or(false) {
+    conn
       .call(
         move |conn: &mut rusqlite::Connection| -> Result<Vec<String>, trailbase_sqlite::Error> {
           let tx = conn.transaction()?;
@@ -211,8 +244,7 @@ pub async fn record_transactions_handler(
       )
       .await?
   } else {
-    state
-      .conn()
+    conn
       .call(
         move |conn: &mut rusqlite::Connection| -> Result<Vec<String>, trailbase_sqlite::Error> {
           let mut ids: Vec<String> = vec![];
@@ -243,14 +275,8 @@ fn extract_record_id(value: rusqlite::types::Value) -> Result<String, trailbase_
 }
 
 #[inline]
-fn get_api(state: &AppState, api_name: &str) -> Result<RecordApi, RecordError> {
-  let Some(api) = state.lookup_record_api(api_name) else {
-    return Err(RecordError::ApiNotFound);
-  };
-  if !api.is_table() {
-    return Err(RecordError::ApiRequiresTable);
-  }
-  return Ok(api);
+fn get_db_name(name: &QualifiedName) -> &str {
+  return name.database_schema.as_deref().unwrap_or("main");
 }
 
 #[inline]
diff --git a/crates/core/src/server/mod.rs b/crates/core/src/server/mod.rs
index 2b26a2c6..add49eb3 100644
--- a/crates/core/src/server/mod.rs
+++ b/crates/core/src/server/mod.rs
@@ -249,9 +249,13 @@ impl Server {
           // Re-apply migrations. This needs to happen before reloading the config, which is
           // consistent with the startup order. Otherwise, we may validate a configuration
           // against a stale database schema.
+          //
+          // TODO: Right now we're only re-applying main migrations.
           let user_migrations_path = state.data_dir().migrations_path();
           match state
-            .conn()
+            .connection_manager()
+            .main_entry()
+            .connection
             .call(|conn: &mut rusqlite::Connection| {
               return crate::migrations::apply_main_migrations(conn, Some(user_migrations_path))
                 .map_err(|err| trailbase_sqlite::Error::Other(err.into()));
diff --git a/crates/core/tests/integration_test.rs b/crates/core/tests/integration_test.rs
index bb747c4d..68a17165 100644
--- a/crates/core/tests/integration_test.rs
+++ b/crates/core/tests/integration_test.rs
@@ -2,6 +2,7 @@ use axum::extract::{Json, State};
 use axum::http::StatusCode;
 use axum_test::TestServer;
 use axum_test::multipart::MultipartForm;
+use std::sync::Arc;
 use tower_cookies::Cookie;
 use trailbase_sqlite::params;
 
@@ -12,7 +13,7 @@ use trailbase::constants::{COOKIE_AUTH_TOKEN, RECORD_API_PATH};
 use trailbase::util::id_to_b64;
 use trailbase::{DataDir, Server, ServerOptions};
 
-pub(crate) async fn add_record_api_config(
+async fn add_record_api_config(
   state: &AppState,
   api: RecordApiConfig,
 ) -> Result<(), anyhow::Error> {
@@ -54,13 +55,13 @@ async fn test_record_apis() {
   assert!(admin_router.is_none());
   assert!(tls.is_none());
 
-  let conn = state.conn();
+  let conn = state.connection_manager().main_entry().connection;
   let logs_conn = state.logs_conn();
 
-  create_chat_message_app_tables(conn).await.unwrap();
+  create_chat_message_app_tables(&conn).await.unwrap();
   state.rebuild_connection_metadata().await.unwrap();
 
-  let room = add_room(conn, "room0").await.unwrap();
+  let room = add_room(&conn, "room0").await.unwrap();
   let password = "Secret!1!!";
   let client_ip = "22.11.22.11";
 
@@ -89,7 +90,7 @@ async fn test_record_apis() {
     .await
     .unwrap();
 
-  add_user_to_room(conn, user_x, room).await.unwrap();
+  add_user_to_room(&conn, user_x, room).await.unwrap();
 
   #[allow(unused_mut)]
   let (_address, mut router) = main_router;
@@ -261,8 +262,8 @@ async fn test_record_apis() {
   assert_eq!(status, 200);
 }
 
-pub async fn create_chat_message_app_tables(
-  conn: &trailbase_sqlite::Connection,
+async fn create_chat_message_app_tables(
+  conn: &Arc<trailbase_sqlite::Connection>,
 ) -> Result<(), anyhow::Error> {
   // Create a messages, chat room and members tables.
   conn
@@ -299,8 +300,8 @@ pub async fn create_chat_message_app_tables(
   return Ok(());
 }
 
-pub async fn add_room(
-  conn: &trailbase_sqlite::Connection,
+async fn add_room(
+  conn: &Arc<trailbase_sqlite::Connection>,
   name: &str,
 ) -> Result<[u8; 16], anyhow::Error> {
   let room: [u8; 16] = conn
@@ -315,8 +316,8 @@ pub async fn add_room(
   return Ok(room);
 }
 
-pub async fn add_user_to_room(
-  conn: &trailbase_sqlite::Connection,
+async fn add_user_to_room(
+  conn: &Arc<trailbase_sqlite::Connection>,
   user: [u8; 16],
   room: [u8; 16],
 ) -> Result<(), anyhow::Error> {
@@ -329,7 +330,7 @@ pub async fn add_user_to_room(
   return Ok(());
 }
 
-pub(crate) async fn create_user_for_test(
+async fn create_user_for_test(
   state: &AppState,
   email: &str,
   password: &str,