diff --git a/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.test.ts b/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.test.ts
index a4e9eb2bb..a75047185 100644
--- a/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.test.ts
+++ b/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.test.ts
@@ -107,6 +107,48 @@ t.test("GET /api/v1/users/:userID/games/:game/:playtype/sessions/best", (t) => {
 		t.end();
 	});
 
+	t.test(
+		"Should return a user's best 100 sessions according to the provided rating alg.",
+		async (t) => {
+			const sessions: SessionDocument[] = [];
+
+			for (let i = 0; i < 200; i++) {
+				sessions.push({
+					sessionID: i.toString(),
+					game: "iidx",
+					playtype: "SP",
+					userID: 1,
+					calculatedData: {
+						ktLampRating: 200 - i,
+						BPI: i,
+					},
+				} as SessionDocument);
+			}
+
+			await db.sessions.remove({});
+			await db.sessions.insert(sessions);
+
+			const res = await mockApi.get(
+				"/api/v1/users/test_zkldi/games/iidx/SP/sessions/best?alg=BPI"
+			);
+
+			t.hasStrict(res.body, {
+				success: true,
+				description: "Retrieved 100 sessions.",
+			});
+
+			t.strictSame(
+				res.body.body.map((e: SessionDocument) => e.sessionID),
+				sessions
+					.slice(100)
+					.reverse()
+					.map((e) => e.sessionID)
+			);
+
+			t.end();
+		}
+	);
+
 	t.end();
 });
 
diff --git a/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.ts b/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.ts
index e1bc8b446..d42048c32 100644
--- a/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.ts
+++ b/server/src/server/router/api/v1/users/_userID/games/_game/_playtype/sessions/router.ts
@@ -3,6 +3,7 @@ import db from "external/mongo/db";
 import { SYMBOL_TachiData } from "lib/constants/tachi";
 import { SearchSessions } from "lib/search/search";
 import { GetGamePTConfig } from "tachi-common";
+import { CheckStrSessionAlg, SessionRatingAlgs } from "utils/string-checks";
 
 const router: Router = Router({ mergeParams: true });
 
@@ -37,7 +38,6 @@ router.get("/", async (req, res) => {
  * for that game.
  *
  * @param alg - An override to specify a different algorithm for that game.
- * UNIMPLEMENTED!!!
  * @name GET /api/v1/users/:userID/games/:game/:playtype/sessions/best
  */
 router.get("/best", async (req, res) => {
@@ -46,6 +46,22 @@ router.get("/best", async (req, res) => {
 	const playtype = req[SYMBOL_TachiData]!.playtype!;
 	const gptConfig = GetGamePTConfig(game, playtype);
 
+	let alg = gptConfig.defaultSessionRatingAlg;
+	if (typeof req.query.alg === "string") {
+		const userAlg = CheckStrSessionAlg(game, playtype, req.query.alg);
+
+		if (userAlg === null) {
+			return res.status(400).json({
+				success: false,
+				description: `Invalid algorithm '${
+					req.query.alg
+				}' provided. Expected any of ${gptConfig.sessionRatingAlgs.join(", ")}.`,
+			});
+		}
+
+		alg = userAlg;
+	}
+
 	const sessions = await db.sessions.find(
 		{
 			userID: user.id,
@@ -55,7 +71,7 @@ router.get("/best", async (req, res) => {
 		{
 			limit: 100,
 			sort: {
-				[`calculatedData.${gptConfig.defaultSessionRatingAlg}`]: -1,
+				[`calculatedData.${alg}`]: -1,
 			},
 		}
 	);