diff --git a/persistence/schema.sql b/persistence/schema.sql
index 575a146..545293e 100644
--- a/persistence/schema.sql
+++ b/persistence/schema.sql
@@ -49,6 +49,8 @@ create table tweets (rowid integer primary key,
     is_stub boolean default 0,
 
     is_content_downloaded boolean default 0,
+    is_conversation_scraped boolean default 0,
+    last_scraped_at integer not null default 0,
     foreign key(user_id) references users(id)
 );
 
diff --git a/persistence/tweet_queries.go b/persistence/tweet_queries.go
index 69e6676..e37401d 100644
--- a/persistence/tweet_queries.go
+++ b/persistence/tweet_queries.go
@@ -16,18 +16,20 @@ func (p Profile) SaveTweet(t scraper.Tweet) error {
         return err
     }
     _, err = db.Exec(`
-        insert into tweets (id, user_id, text, posted_at, num_likes, num_retweets, num_replies, num_quote_tweets, in_reply_to_id, quoted_tweet_id, mentions, reply_mentions, hashtags, tombstone_type, is_stub, is_content_downloaded)
-        values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, (select rowid from tombstone_types where short_name=?), ?, ?)
+        insert into tweets (id, user_id, text, posted_at, num_likes, num_retweets, num_replies, num_quote_tweets, in_reply_to_id, quoted_tweet_id, mentions, reply_mentions, hashtags, tombstone_type, is_stub, is_content_downloaded, is_conversation_scraped, last_scraped_at)
+        values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, (select rowid from tombstone_types where short_name=?), ?, ?, ?, ?)
             on conflict do update
            set num_likes=?,
                num_retweets=?,
                num_replies=?,
                num_quote_tweets=?,
                is_stub=(is_stub and ?),
-               is_content_downloaded=(is_content_downloaded or ?)
+               is_content_downloaded=(is_content_downloaded or ?),
+               is_conversation_scraped=(is_conversation_scraped or ?),
+               last_scraped_at=max(last_scraped_at, ?)
         `,
-        t.ID, t.UserID, t.Text, t.PostedAt.Unix(), t.NumLikes, t.NumRetweets, t.NumReplies, t.NumQuoteTweets, t.InReplyToID, t.QuotedTweetID, scraper.JoinArrayOfHandles(t.Mentions), scraper.JoinArrayOfHandles(t.ReplyMentions), strings.Join(t.Hashtags, ","), t.TombstoneType, t.IsStub, t.IsContentDownloaded,
-        t.NumLikes, t.NumRetweets, t.NumReplies, t.NumQuoteTweets, t.IsStub, t.IsContentDownloaded,
+        t.ID, t.UserID, t.Text, t.PostedAt.Unix(), t.NumLikes, t.NumRetweets, t.NumReplies, t.NumQuoteTweets, t.InReplyToID, t.QuotedTweetID, scraper.JoinArrayOfHandles(t.Mentions), scraper.JoinArrayOfHandles(t.ReplyMentions), strings.Join(t.Hashtags, ","), t.TombstoneType, t.IsStub, t.IsContentDownloaded, t.IsConversationScraped, t.LastScrapedAt.Unix(),
+        t.NumLikes, t.NumRetweets, t.NumReplies, t.NumQuoteTweets, t.IsStub, t.IsContentDownloaded, t.IsConversationScraped, t.LastScrapedAt.Unix(),
     )
 
     if err != nil {
@@ -90,7 +92,7 @@ func (p Profile) GetTweetById(id scraper.TweetID) (scraper.Tweet, error) {
     db := p.DB
 
     stmt, err := db.Prepare(`
-        select id, user_id, text, posted_at, num_likes, num_retweets, num_replies, num_quote_tweets, in_reply_to_id, quoted_tweet_id, mentions, reply_mentions, hashtags, ifnull(tombstone_types.short_name, ""), is_stub, is_content_downloaded
+        select id, user_id, text, posted_at, num_likes, num_retweets, num_replies, num_quote_tweets, in_reply_to_id, quoted_tweet_id, mentions, reply_mentions, hashtags, ifnull(tombstone_types.short_name, ""), is_stub, is_content_downloaded, is_conversation_scraped, last_scraped_at
           from tweets left join tombstone_types on tweets.tombstone_type = tombstone_types.rowid
          where id = ?
     `)
@@ -102,17 +104,20 @@ func (p Profile) GetTweetById(id scraper.TweetID) (scraper.Tweet, error) {
 
     var t scraper.Tweet
     var postedAt int
+    var last_scraped_at int
     var mentions string
     var reply_mentions string
     var hashtags string
 
     row := stmt.QueryRow(id)
-    err = row.Scan(&t.ID, &t.UserID, &t.Text, &postedAt, &t.NumLikes, &t.NumRetweets, &t.NumReplies, &t.NumQuoteTweets, &t.InReplyToID, &t.QuotedTweetID, &mentions, &reply_mentions, &hashtags, &t.TombstoneType, &t.IsStub, &t.IsContentDownloaded)
+    err = row.Scan(&t.ID, &t.UserID, &t.Text, &postedAt, &t.NumLikes, &t.NumRetweets, &t.NumReplies, &t.NumQuoteTweets, &t.InReplyToID, &t.QuotedTweetID, &mentions, &reply_mentions, &hashtags, &t.TombstoneType, &t.IsStub, &t.IsContentDownloaded, &t.IsConversationScraped, &last_scraped_at)
     if err != nil {
         return t, err
     }
 
     t.PostedAt = time.Unix(int64(postedAt), 0)  // args are `seconds` and `nanoseconds`
+    t.LastScrapedAt = time.Unix(int64(last_scraped_at), 0)
+
     t.Mentions = []scraper.UserHandle{}
     for _, m := range strings.Split(mentions, ",") {
         if m != "" {
diff --git a/persistence/tweet_queries_test.go b/persistence/tweet_queries_test.go
index 81c4db6..8c7e13c 100644
--- a/persistence/tweet_queries_test.go
+++ b/persistence/tweet_queries_test.go
@@ -2,6 +2,7 @@ package persistence_test
 
 import (
     "testing"
+    "time"
 
     "github.com/go-test/deep"
 )
@@ -75,6 +76,8 @@ func TestNoWorseningTweet(t *testing.T) {
     tweet := create_dummy_tweet()
     tweet.IsContentDownloaded = true
     tweet.IsStub = false
+    tweet.IsConversationScraped = true
+    tweet.LastScrapedAt = time.Unix(1000, 0)
 
     // Save the tweet
     err := profile.SaveTweet(tweet)
@@ -85,6 +88,8 @@ func TestNoWorseningTweet(t *testing.T) {
     // Worsen the tweet and re-save it
     tweet.IsContentDownloaded = false
     tweet.IsStub = true
+    tweet.IsConversationScraped = false
+    tweet.LastScrapedAt = time.Unix(500, 0)
     err = profile.SaveTweet(tweet)
     if err != nil {
         t.Fatalf("Failed to save the tweet: %s", err.Error())
@@ -102,6 +107,77 @@ func TestNoWorseningTweet(t *testing.T) {
     if new_tweet.IsContentDownloaded != true {
         t.Errorf("Should have preserved is-content-downloaded status")
     }
+    if new_tweet.IsConversationScraped == false {
+        t.Errorf("Should have preserved is-conversation-scraped status")
+    }
+    if new_tweet.LastScrapedAt.Unix() != 1000 {
+        t.Errorf("Should have preserved last-scraped-at time")
+    }
+}
+
+func TestModifyTweet(t *testing.T) {
+    profile_path := "test_profiles/TestTweetQueries"
+    profile := create_or_load_profile(profile_path)
+
+    tweet := create_dummy_tweet()
+    tweet.NumLikes = 1000
+    tweet.NumRetweets = 2000
+    tweet.NumReplies = 3000
+    tweet.NumQuoteTweets = 4000
+    tweet.IsStub = true
+    tweet.IsContentDownloaded = false
+    tweet.IsConversationScraped = false
+    tweet.LastScrapedAt = time.Unix(1000, 0)
+
+    err := profile.SaveTweet(tweet)
+    if err != nil {
+        t.Fatalf("Failed to save the tweet: %s", err.Error())
+    }
+
+    tweet.NumLikes = 1500
+    tweet.NumRetweets = 2500
+    tweet.NumReplies = 3500
+    tweet.NumQuoteTweets = 4500
+    tweet.IsStub = false
+    tweet.IsContentDownloaded = true
+    tweet.IsConversationScraped = true
+    tweet.LastScrapedAt = time.Unix(2000, 0)
+
+    err = profile.SaveTweet(tweet)
+    if err != nil {
+        t.Fatalf("Failed to re-save the tweet: %s", err.Error())
+    }
+
+    // Reload the tweet
+    new_tweet, err := profile.GetTweetById(tweet.ID)
+    if err != nil {
+        t.Fatalf("Failed to load the tweet: %s", err.Error())
+    }
+
+    if new_tweet.NumLikes != 1500 {
+        t.Errorf("Expected %d likes, got %d", 1500, new_tweet.NumLikes)
+    }
+    if new_tweet.NumRetweets != 2500 {
+        t.Errorf("Expected %d retweets, got %d", 2500, new_tweet.NumRetweets)
+    }
+    if new_tweet.NumReplies != 3500 {
+        t.Errorf("Expected %d replies, got %d", 1500, new_tweet.NumReplies)
+    }
+    if new_tweet.NumQuoteTweets != 4500 {
+        t.Errorf("Expected %d quote tweets, got %d", 4500, new_tweet.NumQuoteTweets)
+    }
+    if new_tweet.IsStub != false {
+        t.Errorf("Expected tweet to not be a stub, but it was")
+    }
+    if new_tweet.IsContentDownloaded != true {
+        t.Errorf("Expected tweet content to be downloaded, but it wasn't")
+    }
+    if new_tweet.IsConversationScraped != true {
+        t.Errorf("Expected conversation to be scraped, but it wasn't")
+    }
+    if new_tweet.LastScrapedAt.Unix() != 2000 {
+        t.Errorf("Expected tweet to be scraped at %d (unix timestamp), but got %d", 2000, new_tweet.LastScrapedAt.Unix())
+    }
 }
 
 /**
diff --git a/persistence/utils_test.go b/persistence/utils_test.go
index 66ef18e..48bb5de 100644
--- a/persistence/utils_test.go
+++ b/persistence/utils_test.go
@@ -168,6 +168,8 @@ func create_stable_tweet() scraper.Tweet {
 		Polls: []scraper.Poll{
 			create_poll_from_id(-1),
 		},
+		IsConversationScraped: true,
+		LastScrapedAt: time.Unix(100000000, 0),
 	}
 }
 
diff --git a/persistence/versions.go b/persistence/versions.go
index bbfcd8f..40b21f5 100644
--- a/persistence/versions.go
+++ b/persistence/versions.go
@@ -8,7 +8,7 @@ import (
 )
 
 
-const ENGINE_DATABASE_VERSION = 1
+const ENGINE_DATABASE_VERSION = 2
 
 
 type VersionMismatchError struct {
@@ -48,7 +48,9 @@ var MIGRATIONS = []string{
     last_scraped_at integer not null,
 
     foreign key(tweet_id) references tweets(id)
-);`,
+	);`,
+`alter table tweets add column is_conversation_scraped boolean default 0;
+	alter table tweets add column last_scraped_at integer not null default 0`,
 }
 
 /**
diff --git a/scraper/tweet.go b/scraper/tweet.go
index bac5dca..74f21f2 100644
--- a/scraper/tweet.go
+++ b/scraper/tweet.go
@@ -37,6 +37,8 @@ type Tweet struct {
 	IsStub bool
 
 	IsContentDownloaded bool
+	IsConversationScraped bool
+	LastScrapedAt time.Time
 }