diff --git a/company/misc.go b/company/misc.go
index a457d06..e867988 100644
--- a/company/misc.go
+++ b/company/misc.go
@@ -6,7 +6,7 @@ import (
 )
 
 type OID struct {
-	ID primitive.ObjectID `json:"id"`
+	ID primitive.ObjectID `json:"_id"`
 }
 
 type AlternateHR struct {
diff --git a/opportunity/application.go b/opportunity/application.go
index 2db2957..61a2e3c 100644
--- a/opportunity/application.go
+++ b/opportunity/application.go
@@ -5,15 +5,9 @@ import (
 )
 
 type Application struct {
-	ID               primitive.ObjectID `json:"id,omitempty"`
-	Opportunity      primitive.ObjectID `json:"opportunity,omitempty"`
-	Student          primitive.ObjectID `json:"student,omitempty"`
-	Resume           primitive.ObjectID `json:"resume,omitempty"`
-	DetailsRequested []DetailsRequested `json:"details_requested,omitempty"`
-}
-
-type DetailsRequested struct {
-	Key   string `json:"key,omitempty"`
-	Type  string `json:"type,omitempty"`
-	Value string `json:"value,omitempty"`
+	ID                     primitive.ObjectID     `bson:"_id" json:"_id,omitempty"`
+	Opportunity            primitive.ObjectID     `bson:"opportunity" json:"opportunity,omitempty"`
+	Student                primitive.ObjectID     `bson:"student" json:"student,omitempty"`
+	Resume                 primitive.ObjectID     `bson:"resume" json:"resume,omitempty"`
+	DetailsRequestedSchema map[string]interface{} `bson:"detailsRequestedSchema" json:"detailsRequestedSchema"`
 }
diff --git a/opportunity/criteria.go b/opportunity/criteria.go
index 405e3b7..d89f706 100644
--- a/opportunity/criteria.go
+++ b/opportunity/criteria.go
@@ -6,7 +6,7 @@ import (
 )
 
 type Criteria struct {
-	ID            primitive.ObjectID `bson:"id" json:"id,omitempty"`
+	ID            primitive.ObjectID `bson:"_id" json:"_id,omitempty"`
 	Xth           float32            `bson:"xth" json:"xth,omitempty"`
 	XIIth         float32            `bson:"xiith" json:"xiith,omitempty"`
 	CGPA          float32            `bson:"cgpa" json:"cgpa,omitempty"`
diff --git a/opportunity/opportunity.go b/opportunity/opportunity.go
index 18768f1..1b7fe3d 100644
--- a/opportunity/opportunity.go
+++ b/opportunity/opportunity.go
@@ -13,7 +13,7 @@ const (
 )
 
 type Opportunity struct {
-	ID                     primitive.ObjectID     `bson:"id" json:"id,omitempty"`
+	ID                     primitive.ObjectID     `bson:"_id" json:"_id,omitempty"`
 	Company                primitive.ObjectID     `bson:"company" json:"company,omitempty"`
 	Profiles               []primitive.ObjectID   `bson:"profile" json:"profile,omitempty"`
 	DetailsRequestedSchema map[string]interface{} `bson:"detailsRequestedSchema" json:"detailsRequestedSchema"`
diff --git a/opportunity/slot.go b/opportunity/slot.go
index 71be3c6..7d0a94b 100644
--- a/opportunity/slot.go
+++ b/opportunity/slot.go
@@ -3,6 +3,7 @@ package opportunity
 import "go.mongodb.org/mongo-driver/bson/primitive"
 
 type Slot struct {
+	ID                  primitive.ObjectID `bson:"_id" json:"_id,omitempty"`
 	Day                 primitive.DateTime `bson:"day" json:"day,omitempty"`
 	StartDate           primitive.DateTime `bson:"start_date" json:"start_date,omitempty"`
 	EndDate             primitive.DateTime `bson:"end_date" json:"end_date,omitempty"`
@@ -11,4 +12,8 @@ type Slot struct {
 	MaxInterviews       int                `bson:"max_interviews" json:"max_interviews,omitempty"`
 	PreferenceStartTime primitive.DateTime `bson:"preference_start_time" json:"preference_start_time,omitempty"`
 	PreferenceEndTime   primitive.DateTime `bson:"preference_end_time" json:"preference_end_time,omitempty"`
+
+	// metadata
+	CreatedAt primitive.DateTime `bson:"createdAt" json:"createdAt,omitempty"`
+	UpdatedAt primitive.DateTime `bson:"updatedAt" json:"updatedAt,omitempty"`
 }