diff --git a/src/main/java/com/codzilla/backend/Matchmaking/MatchStatus.java b/src/main/java/com/codzilla/backend/Matchmaking/MatchStatus.java
new file mode 100644
index 0000000..6d15d80
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/MatchStatus.java
@@ -0,0 +1,6 @@
+package com.codzilla.backend.Matchmaking;
+
+public enum MatchStatus {
+    WAITING,
+    NOT_IN_QUEUE
+}
\ No newline at end of file
diff --git a/src/main/java/com/codzilla/backend/Matchmaking/MatchStatusResult.java b/src/main/java/com/codzilla/backend/Matchmaking/MatchStatusResult.java
new file mode 100644
index 0000000..4b2d8f5
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/MatchStatusResult.java
@@ -0,0 +1,7 @@
+package com.codzilla.backend.Matchmaking;
+
+public record MatchStatusResult(
+        MatchStatus status,
+        int queueSize,
+        long waitingSeconds
+) {}
\ No newline at end of file
diff --git a/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingController.java b/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingController.java
new file mode 100644
index 0000000..8951430
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingController.java
@@ -0,0 +1,52 @@
+package com.codzilla.backend.Matchmaking;
+
+import com.codzilla.backend.Matchmaking.dto.MatchStatusDTO;
+import com.codzilla.backend.User.User;
+import com.codzilla.backend.User.UserRepository;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.core.userdetails.UsernameNotFoundException;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.UUID;
+
+@RestController
+@RequestMapping("/matchmaking")
+public class MatchmakingController {
+
+    private final MatchmakingService matchmakingService;
+    private final UserRepository userRepository;
+
+    public MatchmakingController(MatchmakingService matchmakingService,
+                                 UserRepository userRepository) {
+        this.matchmakingService = matchmakingService;
+        this.userRepository = userRepository;
+    }
+
+    private UUID resolveUserId(User principal) {
+        return userRepository.findIdByEmail(principal.getEmail())
+                .orElseThrow(() -> new UsernameNotFoundException("User not found"));
+    }
+
+    @PostMapping("/queue")
+    public ResponseEntity<Void> enterQueue(@AuthenticationPrincipal User user) {
+        matchmakingService.enterQueue(resolveUserId(user));
+        return ResponseEntity.ok().build();
+    }
+
+    @DeleteMapping("/queue")
+    public ResponseEntity<Void> leaveQueue(@AuthenticationPrincipal User user) {
+        matchmakingService.leaveQueue(resolveUserId(user));
+        return ResponseEntity.ok().build();
+    }
+
+    @GetMapping("/queue/status")
+    public ResponseEntity<MatchStatusDTO> queueStatus(@AuthenticationPrincipal User user) {
+        MatchStatusResult result = matchmakingService.queueStatus(resolveUserId(user));
+        return ResponseEntity.ok(new MatchStatusDTO(
+                result.status(),
+                result.queueSize(),
+                result.waitingSeconds()
+        ));
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingScheduler.java b/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingScheduler.java
new file mode 100644
index 0000000..48412eb
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingScheduler.java
@@ -0,0 +1,21 @@
+package com.codzilla.backend.Matchmaking;
+
+import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+@Component
+@EnableScheduling
+public class MatchmakingScheduler {
+
+    private final MatchmakingService matchmakingService;
+
+    public MatchmakingScheduler(MatchmakingService matchmakingService) {
+        this.matchmakingService = matchmakingService;
+    }
+
+    @Scheduled(fixedDelay = 2000)
+    public void runMatchmaking() {
+        matchmakingService.runMatchmaking();
+    }
+}
diff --git a/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingService.java b/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingService.java
new file mode 100644
index 0000000..b499913
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/MatchmakingService.java
@@ -0,0 +1,92 @@
+package com.codzilla.backend.Matchmaking;
+
+import com.codzilla.backend.Authentication.Exceptions.UserNotFoundException;
+import com.codzilla.backend.User.UserRepository;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+
+import java.time.Instant;
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+
+@Slf4j
+@Service
+public class MatchmakingService {
+
+    public static final int BASE_WINDOW = 50;
+    public static final int WAVE_STEP   = 25;
+    public static final int MAX_WINDOW  = 400;
+
+    private final ConcurrentHashMap<UUID, QueueEntry> queue = new ConcurrentHashMap<>();
+    private final UserRepository userRepository;
+
+    public MatchmakingService(UserRepository userRepository) {
+        this.userRepository = userRepository;
+    }
+
+    public void enterQueue(UUID userId) {
+        var user = userRepository.findById(userId)
+                .orElseThrow(UserNotFoundException::new);
+        queue.put(userId, new QueueEntry(userId, user.getRating(), Instant.now()));
+        log.info("[MM] User {} (rating={}) entered queue. Size: {}", userId, user.getRating(), queue.size());
+    }
+
+    public void leaveQueue(UUID userId) {
+        queue.remove(userId);
+        log.info("[MM] User {} left queue. Size: {}", userId, queue.size());
+    }
+
+    public MatchStatusResult queueStatus(UUID userId) {
+        QueueEntry entry = queue.get(userId);
+        if (entry == null) {
+            return new MatchStatusResult(MatchStatus.NOT_IN_QUEUE, queue.size(), 0);
+        }
+        long waiting = Instant.now().getEpochSecond() - entry.joinedAt().getEpochSecond();
+        return new MatchStatusResult(MatchStatus.WAITING, queue.size(), waiting);
+    }
+
+    public synchronized void runMatchmaking() {
+        if (queue.size() < 2) return;
+
+        List<QueueEntry> sorted = new ArrayList<>(queue.values());
+        sorted.sort(Comparator.comparingInt(QueueEntry::rating));
+
+        Set<UUID> matched = new HashSet<>();
+
+        for (int i = 0; i < sorted.size() - 1; i++) {
+            QueueEntry a = sorted.get(i);
+            if (matched.contains(a.userId())) continue;
+
+            for (int j = i + 1; j < sorted.size(); j++) {
+                QueueEntry b = sorted.get(j);
+                if (matched.contains(b.userId())) continue;
+
+                int diff   = Math.abs(a.rating() - b.rating());
+                int window = Math.min(a.ratingWindow(), b.ratingWindow());
+
+                if (diff <= window) {
+                    pair(a.userId(), b.userId());
+                    matched.add(a.userId());
+                    matched.add(b.userId());
+                    break;
+                }
+
+                if (diff > MAX_WINDOW) break;
+            }
+        }
+    }
+
+    private void pair(UUID a, UUID b) {
+        QueueEntry removedA = queue.remove(a);
+        QueueEntry removedB = queue.remove(b);
+
+        if (removedA == null || removedB == null) {
+            if (removedA != null) queue.put(a, removedA);
+            if (removedB != null) queue.put(b, removedB);
+            log.warn("[MM] Pairing cancelled: one of users left queue ({} or {})", a, b);
+            return;
+        }
+        // TODO implement create session call
+        log.info("[MM] Paired: {} vs {}", a, b);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/codzilla/backend/Matchmaking/QueueEntry.java b/src/main/java/com/codzilla/backend/Matchmaking/QueueEntry.java
new file mode 100644
index 0000000..567f5d4
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/QueueEntry.java
@@ -0,0 +1,16 @@
+package com.codzilla.backend.Matchmaking;
+
+import java.time.Instant;
+import java.util.UUID;
+
+public record QueueEntry(
+        UUID userId,
+        int rating,
+        Instant joinedAt
+) {
+    public int ratingWindow() {
+        long secondsWaiting = Instant.now().getEpochSecond() - joinedAt.getEpochSecond();
+        int wave = (int) (secondsWaiting / 5) * MatchmakingService.WAVE_STEP;
+        return Math.min(wave + MatchmakingService.BASE_WINDOW, MatchmakingService.MAX_WINDOW);
+    }
+}
diff --git a/src/main/java/com/codzilla/backend/Matchmaking/dto/MatchStatusDTO.java b/src/main/java/com/codzilla/backend/Matchmaking/dto/MatchStatusDTO.java
new file mode 100644
index 0000000..1eb2f00
--- /dev/null
+++ b/src/main/java/com/codzilla/backend/Matchmaking/dto/MatchStatusDTO.java
@@ -0,0 +1,9 @@
+package com.codzilla.backend.Matchmaking.dto;
+
+import com.codzilla.backend.Matchmaking.MatchStatus;
+
+public record MatchStatusDTO(
+        MatchStatus status,
+        int queueSize,
+        long waitingSeconds
+) {}
\ No newline at end of file
diff --git a/src/test/java/com/codzilla/backend/Matchmaking/MatchmakingServiceTest.java b/src/test/java/com/codzilla/backend/Matchmaking/MatchmakingServiceTest.java
new file mode 100644
index 0000000..9ffb7ed
--- /dev/null
+++ b/src/test/java/com/codzilla/backend/Matchmaking/MatchmakingServiceTest.java
@@ -0,0 +1,153 @@
+package com.codzilla.backend.Matchmaking;
+
+import com.codzilla.backend.User.User;
+import com.codzilla.backend.User.UserRepository;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.lang.reflect.Field;
+import java.time.Instant;
+import java.util.Optional;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+class MatchmakingServiceTest {
+
+    @Mock
+    private UserRepository userRepository;
+
+    private MatchmakingService service;
+
+    private ConcurrentHashMap<UUID, QueueEntry> queue;
+
+    @BeforeEach
+    @SuppressWarnings("unchecked")
+    void setUp() throws Exception {
+        service = new MatchmakingService(userRepository);
+
+        Field queueField = MatchmakingService.class.getDeclaredField("queue");
+        queueField.setAccessible(true);
+        queue = (ConcurrentHashMap<UUID, QueueEntry>) queueField.get(service);
+    }
+
+    private QueueEntry entry(UUID userId, int rating, long waitingSeconds) {
+        return new QueueEntry(userId, rating, Instant.now().minusSeconds(waitingSeconds));
+    }
+
+    private UUID addToQueue(int rating, long waitingSeconds) {
+        UUID id = UUID.randomUUID();
+        queue.put(id, entry(id, rating, waitingSeconds));
+        return id;
+    }
+
+    private UUID addToQueue(int rating) {
+        return addToQueue(rating, 0);
+    }
+
+    private UUID mockUser(int rating) {
+        UUID id = UUID.randomUUID();
+        User user = User.builder().id(id).rating(rating).email(id + "@test.com").build();
+        when(userRepository.findById(id)).thenReturn(Optional.of(user));
+        return id;
+    }
+
+    @Test
+    @DisplayName("enterQueue: игрок добавляется в очередь с правильным рейтингом")
+    void enterQueue_addsUserWithCorrectRating() {
+        UUID userId = mockUser(1200);
+
+        service.enterQueue(userId);
+
+        assertThat(queue).containsKey(userId);
+        assertThat(queue.get(userId).rating()).isEqualTo(1200);
+    }
+
+    @Test
+    @DisplayName("enterQueue: повторный вызов обновляет запись (рейтинг мог измениться)")
+    void enterQueue_updatesExistingEntry() {
+        UUID userId = mockUser(1200);
+        service.enterQueue(userId);
+
+        User updated = User.builder().id(userId).rating(1300).email(userId + "@test.com").build();
+        when(userRepository.findById(userId)).thenReturn(Optional.of(updated));
+        service.enterQueue(userId);
+
+        assertThat(queue.get(userId).rating()).isEqualTo(1300);
+    }
+
+    @Test
+    @DisplayName("leaveQueue: игрок убирается из очереди")
+    void leaveQueue_removesUser() {
+        UUID userId = addToQueue(1000);
+
+        service.leaveQueue(userId);
+
+        assertThat(queue).doesNotContainKey(userId);
+    }
+
+    @Test
+    @DisplayName("leaveQueue: вызов для игрока не в очереди не бросает исключение")
+    void leaveQueue_nonExistentUser_doesNotThrow() {
+        assertThatNoException().isThrownBy(() -> service.leaveQueue(UUID.randomUUID()));
+    }
+
+    @Test
+    @DisplayName("runMatchmaking: игроки с разницей рейтинга больше окна НЕ спариваются")
+    void runMatchmaking_doesNotPairPlayersOutsideWindow() {
+        UUID a = addToQueue(1000);
+        UUID b = addToQueue(1100);
+
+        service.runMatchmaking();
+
+        assertThat(queue).containsKey(a).containsKey(b);
+    }
+
+    @Test
+    @DisplayName("runMatchmaking: меньше двух игроков — ничего не происходит")
+    void runMatchmaking_lessThanTwoPlayers_doesNothing() {
+        addToQueue(1000);
+
+        service.runMatchmaking();
+
+        assertThat(queue).hasSize(1);
+    }
+
+    @Test
+    @DisplayName("runMatchmaking: окно не превышает MAX_WINDOW даже при долгом ожидании")
+    void runMatchmaking_windowCappedAtMaxWindow() {
+        UUID a = addToQueue(1000, 10000);
+        UUID b = addToQueue(1500);
+
+        service.runMatchmaking();
+
+        assertThat(queue).containsKey(a).containsKey(b);
+    }
+
+    @Test
+    @DisplayName("queueStatus: игрок в очереди — статус WAITING")
+    void queueStatus_playerInQueue_returnsWaiting() {
+        UUID userId = addToQueue(1000, 5);
+
+        var status = service.queueStatus(userId);
+
+        assertThat(status.status()).isEqualTo(MatchStatus.WAITING);
+        assertThat(status.queueSize()).isEqualTo(1);
+        assertThat(status.waitingSeconds()).isGreaterThanOrEqualTo(5);
+    }
+
+    @Test
+    @DisplayName("queueStatus: игрок не в очереди — статус NOT_IN_QUEUE")
+    void queueStatus_playerNotInQueue_returnsNotInQueue() {
+        var status = service.queueStatus(UUID.randomUUID());
+
+        assertThat(status.status()).isEqualTo(MatchStatus.NOT_IN_QUEUE);
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/com/codzilla/backend/Matchmaking/QueueEntryTest.java b/src/test/java/com/codzilla/backend/Matchmaking/QueueEntryTest.java
new file mode 100644
index 0000000..a412c87
--- /dev/null
+++ b/src/test/java/com/codzilla/backend/Matchmaking/QueueEntryTest.java
@@ -0,0 +1,62 @@
+package com.codzilla.backend.Matchmaking;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.time.Instant;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class QueueEntryTest {
+
+    private QueueEntry entryWaitingFor(long seconds) {
+        return new QueueEntry(UUID.randomUUID(), 1000, Instant.now().minusSeconds(seconds));
+    }
+
+    @Test
+    @DisplayName("ratingWindow: только что вошёл — базовое окно BASE_WINDOW")
+    void ratingWindow_newEntry_returnsBaseWindow() {
+        QueueEntry entry = entryWaitingFor(0);
+        assertThat(entry.ratingWindow()).isEqualTo(MatchmakingService.BASE_WINDOW);
+    }
+
+    @Test
+    @DisplayName("ratingWindow: ждёт 5 сек — окно BASE_WINDOW + WAVE_STEP")
+    void ratingWindow_after5Seconds_grows() {
+        QueueEntry entry = entryWaitingFor(5);
+        int expected = MatchmakingService.BASE_WINDOW + MatchmakingService.WAVE_STEP;
+        assertThat(entry.ratingWindow()).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("ratingWindow: ждёт 10 сек — окно BASE_WINDOW + 2 * WAVE_STEP")
+    void ratingWindow_after10Seconds_growsFurther() {
+        QueueEntry entry = entryWaitingFor(10);
+        int expected = MatchmakingService.BASE_WINDOW + 2 * MatchmakingService.WAVE_STEP;
+        assertThat(entry.ratingWindow()).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("ratingWindow: очень долгое ожидание — окно не превышает MAX_WINDOW")
+    void ratingWindow_veryLongWait_cappedAtMaxWindow() {
+        QueueEntry entry = entryWaitingFor(100_000);
+        assertThat(entry.ratingWindow()).isEqualTo(MatchmakingService.MAX_WINDOW);
+    }
+
+    @Test
+    @DisplayName("ratingWindow: окно растёт ступенчато — каждые 5 сек")
+    void ratingWindow_growsInSteps() {
+        assertThat(entryWaitingFor(4).ratingWindow())
+                .isEqualTo(MatchmakingService.BASE_WINDOW);
+
+        assertThat(entryWaitingFor(5).ratingWindow())
+                .isEqualTo(MatchmakingService.BASE_WINDOW + MatchmakingService.WAVE_STEP);
+
+        assertThat(entryWaitingFor(9).ratingWindow())
+                .isEqualTo(MatchmakingService.BASE_WINDOW + MatchmakingService.WAVE_STEP);
+
+        assertThat(entryWaitingFor(10).ratingWindow())
+                .isEqualTo(MatchmakingService.BASE_WINDOW + 2 * MatchmakingService.WAVE_STEP);
+    }
+}
\ No newline at end of file