diff --git a/internal/broker/core.go b/internal/broker/core.go
index f9b0a8b..2a1b007 100644
--- a/internal/broker/core.go
+++ b/internal/broker/core.go
@@ -2,10 +2,11 @@ package broker
 
 import (
 	"context"
-	"time"
-
+	"fmt"
 	"github.com/arcana261/ubroker/pkg/ubroker"
 	"github.com/pkg/errors"
+	"sync"
+	"time"
 )
 
 // New creates a new instance of ubroker.Broker
@@ -13,34 +14,215 @@ import (
 // we requeue an unacknowledged/unrequeued message
 // automatically.
 func New(ttl time.Duration) ubroker.Broker {
-	return &core{}
+	return &core{
+		lastMessageId:	 0,
+		ttl:			 ttl,
+		deliveredOnce:   false,
+		isClosed:		 false,
+		mutex: 			 sync.Mutex{},
+		ackedMap:		 make(map[int]bool),
+		messageQueue:	 make([]timedMessage, 900),
+		deliveryChannel: make(chan ubroker.Delivery, 900),
+	}
+}
+
+type timedMessage struct {
+	acknowledge chan bool
+	buildTime 	 time.Time
+	content 	 ubroker.Delivery
 }
 
 type core struct {
-	// TODO: add required fields
+	lastMessageId	int
+	deliveredOnce	bool
+	isClosed		bool
+	mutex 			sync.Mutex
+	ackedMap		map[int]bool
+	ttl				time.Duration
+	messageQueue	[]timedMessage
+	deliveryChannel chan ubroker.Delivery
+}
+
+func (c *core) addMessageToQueue(message ubroker.Message) error {
+
+	if c.isClosed {
+		c.mutex.Unlock()
+		return ubroker.ErrClosed
+	}
+
+	c.lastMessageId = c.lastMessageId + 1
+	var timedM = constructTimedMessage(c.lastMessageId, message)
+	c.messageQueue = append(c.messageQueue, timedM)
+	c.ackedMap[timedM.content.ID] = false
+	c.deliveryChannel <- timedM.content
+
+	c.mutex.Unlock()
+	go c.ensureMessageIsReached(timedM)
+	return nil
+
+}
+
+func (c *core) getMessageFromQueueById(id int) *timedMessage {
+	var index = c.getMessageFromQueueIndexById(id)
+	if index == -1 {
+		return nil
+	} else {
+		return &c.messageQueue[index]
+	}
+}
+
+func (c *core) getMessageFromQueueIndexById(id int) int {
+	for index, m := range c.messageQueue {
+		if id == m.content.ID {
+			return index
+		}
+	}
+	return -1
+}
+
+func (c *core) removeMessageFromQueue(index int) *timedMessage {
+	if index < 0 || index >= len(c.messageQueue) {
+		return nil
+	}
+	var m = c.messageQueue[index]
+	c.messageQueue[index] = c.messageQueue[len(c.messageQueue)-1]
+	c.messageQueue = c.messageQueue[:len(c.messageQueue)-1]
+	return &m
+}
+
+func (c *core) hasCrossedTTL(m timedMessage) bool {
+	return time.Now().Sub(m.buildTime) > c.ttl
+}
+
+func (c *core) ensureMessageIsReached(message timedMessage) {
+	select {
+		case <- time.After(c.ttl):
+			c.mutex.Lock()
+			// remove from mainQ
+			var requeueIndex = c.getMessageFromQueueIndexById(message.content.ID)
+			if requeueIndex == -1 {
+				// We should never reach here
+				fmt.Print("Problem has occurred in ensuring that the message has been reached!")
+			}
+			c.removeMessageFromQueue(requeueIndex)
+			_ = c.addMessageToQueue(message.content.Message)
+		case <- message.acknowledge:
+			c.mutex.Lock()
+			if c.ackedMap[message.content.ID] {
+				c.mutex.Unlock()
+				return
+			}
+			c.mutex.Unlock()
+	}
 }
 
 func (c *core) Delivery(ctx context.Context) (<-chan ubroker.Delivery, error) {
-	// TODO:‌ implement me
-	return nil, errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	if checkContext(ctx) {
+		return nil, ctx.Err()
+	}
+	c.mutex.Lock(); defer c.mutex.Unlock()
+	if c.isClosed {
+		return nil, ubroker.ErrClosed
+	}
+	c.deliveredOnce = true
+	return c.deliveryChannel, nil
 }
 
 func (c *core) Acknowledge(ctx context.Context, id int) error {
-	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method Acknowledge is not implemented")
+	
+	if checkContext(ctx) {
+		return ctx.Err()
+	}
+	
+	c.mutex.Lock(); defer c.mutex.Unlock()
+	if c.isClosed {
+		return ubroker.ErrClosed
+	}
+
+	if !c.deliveredOnce {
+		return errors.Wrap(ubroker.ErrInvalidID, "Message hasn't been delivered!")
+	}
+	if c.ackedMap[id] {
+		return errors.Wrap(ubroker.ErrInvalidID, "Message with this id is already acked!")
+	}
+
+	var m = c.getMessageFromQueueById(id)
+	if m == nil {
+		return errors.Wrap(ubroker.ErrInvalidID, "No corresponding message to the id exists!")
+	}
+	if c.hasCrossedTTL(*m) {
+		return errors.Wrap(ubroker.ErrInvalidID, "Message with this id has invalid time!")
+	}
+
+	c.ackedMap[id] = true
+	m.acknowledge <- true
+	return nil
+
 }
 
 func (c *core) ReQueue(ctx context.Context, id int) error {
-	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method ReQueue is not implemented")
+	
+	if checkContext(ctx) {
+		return ctx.Err()
+	}
+	
+	c.mutex.Lock()
+	if c.isClosed {
+		c.mutex.Unlock()
+		return ubroker.ErrClosed
+	}
+	if !c.deliveredOnce {
+		c.mutex.Unlock()
+		return errors.Wrap(ubroker.ErrInvalidID, "Message hasn't been delivered!")
+	}
+
+	var requeueIndex = c.getMessageFromQueueIndexById(id)
+	if requeueIndex == -1 {
+		c.mutex.Unlock()
+		return errors.Wrap(ubroker.ErrInvalidID, "No corresponding message to the id exists!")
+	}
+
+	var m = *c.removeMessageFromQueue(requeueIndex)
+	return c.addMessageToQueue(m.content.Message)
+
 }
 
 func (c *core) Publish(ctx context.Context, message ubroker.Message) error {
-	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method Publish is not implemented")
+	if checkContext(ctx) {
+		return ctx.Err()
+	}
+	c.mutex.Lock()
+	if c.isClosed {
+		c.mutex.Unlock()
+		return ubroker.ErrClosed
+	}
+	return c.addMessageToQueue(message)
 }
 
 func (c *core) Close() error {
-	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method Close is not implemented")
+	if c.isClosed {
+		return nil
+	}
+	c.mutex.Lock(); defer c.mutex.Unlock()
+	c.isClosed = true
+	close(c.deliveryChannel)
+ 	return nil
 }
+
+func checkContext(ctx context.Context) bool {
+	return map[error]bool {
+    	context.Canceled: true,
+    	context.DeadlineExceeded: true,
+	}[ctx.Err()]
+}
+
+func constructTimedMessage(id int, message ubroker.Message) timedMessage {
+	return timedMessage {
+		acknowledge: make(chan bool, 100),
+		buildTime: 	 time.Now(),
+		content: 	 ubroker.Delivery {
+			Message: message,
+			ID: 	 id,
+		},
+	}
+}
\ No newline at end of file