diff --git a/html/index.php b/html/index.php
index 6c5033d..2fe4998 100644
--- a/html/index.php
+++ b/html/index.php
@@ -1,15 +1,14 @@
 <?php
 
 require_once __DIR__ . "/../core.php";
-require_once __DIR__ . "/../lib/rating.php";
+require_once __DIR__ . "/../lib/pairing.php";
 
 session_start();
 
-$left = getRandomMob();
-$right = getRandomMob();
+$pairing = makeInitialPairing(session_id());
 
-$left["rating"] = getEloForMob($left["id"]);
-$right["rating"] = getEloForMob($right["id"]);
+$left = $pairing[0];
+$right = $pairing[1];
 
 $title = "Test";
 $content = function() use ($left, $right) {
diff --git a/lib/pairing.php b/lib/pairing.php
new file mode 100644
index 0000000..e1ef5c2
--- /dev/null
+++ b/lib/pairing.php
@@ -0,0 +1,103 @@
+<?php
+
+function getRandomMob(): array {
+    global $pdo;
+    $result = $pdo->query("SELECT * FROM mm_mobs WHERE enabled = true");
+    $result = $result->fetchAll(PDO::FETCH_ASSOC);
+    return $result[array_rand($result)];
+}
+
+function findPair(string $session, int $current): array|false {
+    global $pdo;
+
+    error_log($current);
+
+    // language=sql
+    $query = $pdo->prepare(<<<EOF
+            WITH possible_pairings AS (
+                SELECT
+                    pairings.mob,
+                    mob_rating.rating AS mob_rating,
+                    pairings.opponent,
+                    opponent_rating.rating AS opponent_rating
+                FROM (
+                    (
+                        SELECT
+                            mob.id AS mob,
+                            opponent.id AS opponent
+                        FROM mm_mobs mob
+                        CROSS JOIN mm_mobs opponent
+                        WHERE
+                                mob.id != opponent.id
+                            AND mob.enabled
+                            AND opponent.enabled
+                    )
+                    EXCEPT
+                        SELECT
+                            mob,
+                            opponent
+                        FROM mm_matches_of_mob
+                        WHERE session = ?
+                ) AS pairings
+                INNER JOIN mm_current_rating mob_rating 
+                    ON mob_rating.mob = pairings.mob
+                INNER JOIN mm_current_rating opponent_rating 
+                    ON opponent_rating.mob = pairings.opponent
+            )
+            SELECT
+                mob.id AS mob,
+                mob.name AS mob_name,
+                mob.image AS mob_image,
+                pairings_with_difference.mob_rating AS mob_rating,
+                opponent.id AS opponent,
+                opponent.name AS opponent_name,
+                opponent.image AS opponent_image,
+                pairings_with_difference.opponent_rating AS opponent_rating,
+                pairings_with_difference.difference AS rating_difference
+            FROM
+            (
+                SELECT
+                    *,
+                    abs(mob_rating - opponent_rating) AS difference
+                FROM possible_pairings
+            ) AS pairings_with_difference
+            INNER JOIN mm_mobs AS mob 
+                ON pairings_with_difference.mob = mob.id
+            INNER JOIN mm_mobs AS opponent 
+                ON pairings_with_difference.opponent = opponent.id
+            ORDER BY 
+                (pairings_with_difference.mob = ?) DESC, 
+                pairings_with_difference.difference ASC
+            LIMIT 1;
+        EOF);
+    $query->execute([$session, $current]);
+    $result = $query->fetch(PDO::FETCH_ASSOC);
+
+    if ($result === false) {
+        return false;
+    } else {
+        return [
+            [
+                "id" => $result["mob"],
+                "name" => $result["mob_name"],
+                "image" => $result["mob_image"],
+                "rating" => $result["mob_rating"],
+            ],
+            [
+                "id" => $result["opponent"],
+                "name" => $result["opponent_name"],
+                "image" => $result["opponent_image"],
+                "rating" => $result["opponent_rating"],
+            ]
+        ];
+    }
+}
+
+function makeInitialPairing(string $session): array {
+    $current = getRandomMob()["id"];
+    return findPair($session, $current);
+}
+
+function makeFollowUpPairing(string $session, int $winner): array {
+    return findPair($session, $winner);
+}
\ No newline at end of file
diff --git a/lib/rating.php b/lib/rating.php
index d92fdf8..5eb50dd 100644
--- a/lib/rating.php
+++ b/lib/rating.php
@@ -2,13 +2,6 @@
 
 require_once __DIR__ . "/database.php";
 
-function getRandomMob(): array {
-    global $pdo;
-    $result = $pdo->query("SELECT * FROM mm_mobs WHERE enabled = true");
-    $result = $result->fetchAll(PDO::FETCH_ASSOC);
-    return $result[array_rand($result)];
-}
-
 function getEloForMob(int $mob): int {
     global $pdo;
     $query = $pdo->prepare("SELECT * FROM mm_current_rating WHERE mob = ?");