diff --git a/todored/src/routes/board/limit.rs b/todored/src/routes/board/limit.rs
new file mode 100644
index 0000000..a71caa5
--- /dev/null
+++ b/todored/src/routes/board/limit.rs
@@ -0,0 +1,34 @@
+//! Rate limiting for board websocket.
+
+use axum::extract::ws::CloseCode;
+use redis::Connection;
+use crate::outcome::LoggableOutcome;
+
+pub fn rate_limit_by_key(
+	mut rconn: Connection,
+	key: String,
+	increment: usize,
+	limit: usize,
+	expiration_s: usize
+) -> Result<(), CloseCode> {
+	log::trace!("Incrementing rate limit counter for {key:?}...");
+	let response: usize = rconn.cmd("INCRBY")
+		.arg(&key)
+		.arg(increment)
+		.log_err_to_error("Could not increase rate limit counter")
+		.map_err(|_| 1011u16)?;
+
+	log::trace!("Refreshing rate limit counter expiration for {key:?}...");
+	rconn.cmd("EXPIRE")
+		.arg(&key)
+		.arg(expiration_s)
+		.log_err_to_warn("Could not set expiration for rate limit counter");
+
+	log::trace!("Checking rate limit of {limit} / {expiration_s} s for {key:?}...");
+	if response > limit {
+		log::warn!("Hit rate limit of {limit} / {expiration_s} s for {key:?}: counter is at {response}!");
+		return Err(1008u16);
+	}
+
+	Ok(())
+}
diff --git a/todored/src/routes/board/mod.rs b/todored/src/routes/board/mod.rs
index 90c34d2..f4d30cf 100644
--- a/todored/src/routes/board/mod.rs
+++ b/todored/src/routes/board/mod.rs
@@ -7,5 +7,6 @@ pub(self) mod ws_receive;
 pub(self) mod redis_xadd;
 pub(self) mod redis_xread;
 pub(self) mod ws_send;
+pub(self) mod limit;
 
 pub(crate) use self::axum::handler as board_websocket;