diff --git a/services/tunnelbroker/src/constants.rs b/services/tunnelbroker/src/constants.rs
index bfa74d283..eac78e0da 100644
--- a/services/tunnelbroker/src/constants.rs
+++ b/services/tunnelbroker/src/constants.rs
@@ -1,9 +1,28 @@
 use tokio::time::Duration;
 
 pub const GRPC_TX_QUEUE_SIZE: usize = 32;
 pub const GRPC_SERVER_PORT: u16 = 50051;
 pub const GRPC_KEEP_ALIVE_PING_INTERVAL: Duration = Duration::from_secs(3);
 pub const GRPC_KEEP_ALIVE_PING_TIMEOUT: Duration = Duration::from_secs(10);
 
 pub const LOG_LEVEL_ENV_VAR: &str =
   tracing_subscriber::filter::EnvFilter::DEFAULT_ENV;
+
+pub mod dynamodb {
+  // This table holds messages which could not be immediately delivered to
+  // a device.
+  //
+  // - (primary key) = (deviceID: Partition Key, createdAt: Sort Key)
+  // - deviceID: The public key of a device's olm identity key
+  // - payload: Message to be delivered. See shared/tunnelbroker_messages.
+  // - createdAt: UNIX timestamp of when the item was inserted.
+  //     Timestamp is needed to order the messages correctly to the device.
+  pub mod undelivered_messages {
+    pub const TABLE_NAME: &str = "tunnelbroker-undelivered-messages";
+    pub const PARTITION_KEY: &str = "deviceID";
+    pub const DEVICE_ID: &str = "deviceID";
+    pub const PAYLOAD: &str = "payload";
+    pub const CREATED_AT: &str = "createdAt";
+    pub const SORT_KEY: &str = "createdAt";
+  }
+}