diff --git a/src/combine-layouts.rs b/src/combine-layouts.rs
index add1bb2..7e9cc46 100644
--- a/src/combine-layouts.rs
+++ b/src/combine-layouts.rs
@@ -1,4 +1,4 @@
-use db::{LayoutDB, SavedLayout};
+use db::{SqliteLayoutDB, SavedLayout};
 use city::{City, House};
 use itertools::Itertools;
 use crate::combine::transpose_layout;
@@ -13,7 +13,7 @@ enum LastStep {
 }
 
 fn main() {
-    let mut db = LayoutDB::from_file("layouts.sqlite").expect("Failed to load the DB");
+    let mut db = SqliteLayoutDB::from_file("layouts.sqlite").expect("Failed to load the DB");
     eprintln!("Loaded the DB, {} stored layouts", db.layouts().len());
 
     let city = City::read_from_file("01.in", city::INPUT_CITY_WIDTH, city::INPUT_CITY_HEIGHT);
diff --git a/src/combine.rs b/src/combine.rs
index 3f8fc46..16a5ec1 100644
--- a/src/combine.rs
+++ b/src/combine.rs
@@ -1,5 +1,5 @@
 use crate::city;
-use crate::db::{LayoutDB, SavedLayout, MergeLowerBound};
+use crate::db::{SqliteLayoutDB, SavedLayout, MergeLowerBound, LayoutDB};
 use crate::city::{City, House};
 use itertools::Itertools;
 use itertools::iproduct;
@@ -37,7 +37,7 @@ impl CompatibilityCache {
     }
 }
 
-pub fn create_new_best_combination(city: &City, left_layouts: &Vec<SavedLayout>, right_layouts: &Vec<SavedLayout>, db: &mut LayoutDB, cache: &mut CompatibilityCache, transposed: bool) -> bool {
+pub fn create_new_best_combination<TDB: LayoutDB>(city: &City, left_layouts: &Vec<SavedLayout>, right_layouts: &Vec<SavedLayout>, db: &mut TDB, cache: &mut CompatibilityCache, transposed: bool) -> bool {
     let mut best_price = left_layouts.iter().chain(right_layouts.iter())
         .map(|layout| city::get_price(&city, layout.houses()))
         .min();
diff --git a/src/db.rs b/src/db.rs
index 9722b7d..68a6c11 100644
--- a/src/db.rs
+++ b/src/db.rs
@@ -2,8 +2,12 @@ use crate::city::House;
 use rusqlite::{Connection, NO_PARAMS, params, Result};
 use std::collections::HashMap;
 
-pub struct LayoutDB {
+pub struct SqliteLayoutDB {
     connection: Connection,
+    memory_db: MemoryLayoutDB,
+}
+
+pub struct MemoryLayoutDB {
     layouts: Vec<SavedLayout>,
     merge_lower_bounds: HashMap<(usize, usize, bool), MergeLowerBound>,
 }
@@ -57,7 +61,76 @@ impl SavedLayout {
     }
 }
 
-impl LayoutDB {
+impl MemoryLayoutDB {
+    pub fn new(layouts: Vec<SavedLayout>, merge_lower_bounds: HashMap<(usize, usize, bool), MergeLowerBound>) -> Self {
+        MemoryLayoutDB { layouts, merge_lower_bounds }
+    }
+
+    // This exists for use by the SqliteLayoutDB
+    fn add_layout_with_id(&mut self, houses: &Vec<House>, layout_id: usize, fully_optimized: bool) {
+        self.layouts.push(SavedLayout { id: layout_id, houses: houses.clone() });
+    }
+}
+
+pub trait LayoutDB {
+    fn layouts(&self) -> &Vec<SavedLayout>;
+    fn add_layout(&mut self, houses: &Vec<House>, fully_optimized: bool);
+    fn get_merge_lower_bound(&self, left_layout: &SavedLayout, right_layout: &SavedLayout, y_axis: bool) -> Option<u32>;
+    fn add_merge_lower_bound(&mut self, lower_bound: MergeLowerBound);
+    fn add_merge_lower_bounds(&mut self, lower_bounds: Vec<MergeLowerBound>);
+}
+
+impl LayoutDB for MemoryLayoutDB {
+    fn layouts(&self) -> &Vec<SavedLayout> {
+        &self.layouts
+    }
+
+    fn add_layout(&mut self, houses: &Vec<House>, fully_optimized: bool) {
+        let layout_id = self.layouts.iter().map(|x| x.id).max().unwrap_or_default() + 1;
+        self.layouts.push(SavedLayout { id: layout_id, houses: houses.clone() });
+    }
+
+    fn get_merge_lower_bound(&self, left_layout: &SavedLayout, right_layout: &SavedLayout, y_axis: bool) -> Option<u32> {
+        if let Some(bound) = self.merge_lower_bounds.get(&(left_layout.id, right_layout.id, y_axis)) {
+            return Some(bound.price);
+        }
+        None
+    }
+
+    fn add_merge_lower_bound(&mut self, lower_bound: MergeLowerBound) {
+        self.merge_lower_bounds.insert((lower_bound.left_layout_id, lower_bound.right_layout_id, lower_bound.y_axis), lower_bound);
+    }
+
+    fn add_merge_lower_bounds(&mut self, lower_bounds: Vec<MergeLowerBound>) {
+        for lower_bound in lower_bounds {
+            self.merge_lower_bounds.insert((lower_bound.left_layout_id, lower_bound.right_layout_id, lower_bound.y_axis), lower_bound);
+        }
+    }
+}
+
+impl LayoutDB for SqliteLayoutDB {
+    fn layouts(&self) -> &Vec<SavedLayout> {
+        self.layouts()
+    }
+
+    fn add_layout(&mut self, houses: &Vec<House>, fully_optimized: bool) {
+        self.add_layout(houses, fully_optimized).unwrap();
+    }
+
+    fn get_merge_lower_bound(&self, left_layout: &SavedLayout, right_layout: &SavedLayout, y_axis: bool) -> Option<u32> {
+        self.get_merge_lower_bound(left_layout, right_layout, y_axis)
+    }
+
+    fn add_merge_lower_bound(&mut self, lower_bound: MergeLowerBound) {
+        self.add_merge_lower_bound(lower_bound).unwrap()
+    }
+
+    fn add_merge_lower_bounds(&mut self, lower_bounds: Vec<MergeLowerBound>) {
+        self.add_merge_lower_bounds(lower_bounds).unwrap()
+    }
+}
+
+impl SqliteLayoutDB {
     pub fn from_file(filename: &str) -> Result<Self> {
         let connection = Connection::open(filename)?;
         let mut layouts: HashMap<u32, Vec<(u32, u32)>> = HashMap::new();
@@ -102,11 +175,12 @@ impl LayoutDB {
             }
         ).collect();
 
-        Ok(LayoutDB { connection, layouts, merge_lower_bounds: merges })
+        let memory_db = MemoryLayoutDB::new(layouts, merges);
+        Ok(SqliteLayoutDB { connection, memory_db})
     }
 
     pub fn layouts(&self) -> &Vec<SavedLayout> {
-        &self.layouts
+        self.memory_db.layouts()
     }
 
     pub fn add_layout(&mut self, houses: &Vec<House>, fully_optimized: bool) -> Result<()> {
@@ -119,15 +193,12 @@ impl LayoutDB {
                                 params![layout_id, house.x as u32, house.y as u32])?;
         }
         transaction.commit()?;
-        self.layouts.push(SavedLayout { id: layout_id as usize, houses: houses.clone() });
+        self.memory_db.add_layout_with_id(houses, layout_id as usize, fully_optimized);
         Ok(())
     }
 
     pub fn get_merge_lower_bound(&self, left_layout: &SavedLayout, right_layout: &SavedLayout, y_axis: bool) -> Option<u32> {
-        if let Some(bound) = self.merge_lower_bounds.get(&(left_layout.id, right_layout.id, y_axis)) {
-            return Some(bound.price);
-        }
-        None
+        self.memory_db.get_merge_lower_bound(left_layout, right_layout, y_axis)
     }
 
     pub fn add_merge_lower_bound(&mut self, lower_bound: MergeLowerBound) -> Result<()> {
@@ -140,13 +211,13 @@ impl LayoutDB {
                             ],
         )?;
         transaction.commit()?;
-        self.merge_lower_bounds.insert((lower_bound.left_layout_id, lower_bound.right_layout_id, lower_bound.y_axis), lower_bound);
+        self.memory_db.add_merge_lower_bound(lower_bound);
         Ok(())
     }
 
     pub fn add_merge_lower_bounds(&mut self, lower_bounds: Vec<MergeLowerBound>) -> Result<()> {
         let transaction = self.connection.transaction()?;
-        for lower_bound in lower_bounds {
+        for lower_bound in &lower_bounds {
             transaction.execute("INSERT INTO merge_lower_bounds (left_layout_id, right_layout_id, axis, price) VALUES (?1, ?2, ?3, ?4) ON CONFLICT(left_layout_id, right_layout_id) DO UPDATE SET price = ?4",
                                 params![lower_bound.left_layout_id as u32,
                                 lower_bound.right_layout_id as u32,
@@ -154,9 +225,9 @@ impl LayoutDB {
                                 lower_bound.price
                             ],
             )?;
-            self.merge_lower_bounds.insert((lower_bound.left_layout_id, lower_bound.right_layout_id, lower_bound.y_axis), lower_bound);
         }
         transaction.commit()?;
+        self.memory_db.add_merge_lower_bounds(lower_bounds);
         Ok(())
     }
 }
diff --git a/src/import-logs.rs b/src/import-logs.rs
index 11b2448..6e1b430 100644
--- a/src/import-logs.rs
+++ b/src/import-logs.rs
@@ -2,7 +2,7 @@ use std::io;
 use std::io::BufRead;
 use regex::Regex;
 use crate::city::House;
-use crate::db::LayoutDB;
+use crate::db::SqliteLayoutDB;
 
 mod city;
 mod db;
@@ -14,7 +14,7 @@ enum State {
 }
 
 fn main() {
-    let mut db = LayoutDB::from_file("layouts.sqlite").expect("Failed to load the DB");
+    let mut db = SqliteLayoutDB::from_file("layouts.sqlite").expect("Failed to load the DB");
     let stdin = io::stdin();
 
     let price_regex = Regex::new("^Price ([0-9]*), seed ([0-9]*)$").unwrap();
diff --git a/src/main.rs b/src/main.rs
index 2ddd4dc..0640ebe 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,7 +4,7 @@ use std::fmt;
 use std::fmt::Formatter;
 use std::collections::{HashMap, HashSet};
 use city::{HouseLayout, City, House};
-use crate::db::LayoutDB;
+use crate::db::SqliteLayoutDB;
 use crate::population::{build_house_probabilities, populate_from_saved_layout};
 use itertools::Itertools;
 
@@ -23,7 +23,7 @@ enum RunType {
 }
 
 fn main() {
-    let mut db = LayoutDB::from_file("layouts.sqlite").expect("Failed to load the DB");
+    let mut db = SqliteLayoutDB::from_file("layouts.sqlite").expect("Failed to load the DB");
     eprintln!("Loaded the DB, {} stored layouts", db.layouts().len());
 
     let city = City::read_from_file("01.in", city::INPUT_CITY_WIDTH, city::INPUT_CITY_HEIGHT);
diff --git a/src/population.rs b/src/population.rs
index 3a88a41..fa9516e 100644
--- a/src/population.rs
+++ b/src/population.rs
@@ -1,7 +1,7 @@
 use rand::Rng;
 use crate::city::{House, HouseLayout, City};
 use rand::prelude::*;
-use crate::db::{LayoutDB, SavedLayout};
+use crate::db::{SqliteLayoutDB, SavedLayout, LayoutDB};
 use crate::city;
 use std::collections::HashMap;
 use std::ops::Add;
@@ -26,7 +26,7 @@ pub fn populate_random(layout: &mut HouseLayout, rng: &mut StdRng) {
     }
 }
 
-pub fn build_house_probabilities(city: &City, db: &LayoutDB, min_score: f64, max_score: f64) -> (WeightedIndex<f64>, Vec<House>){
+pub fn build_house_probabilities<TDB : LayoutDB>(city: &City, db: &TDB, min_score: f64, max_score: f64) -> (WeightedIndex<f64>, Vec<House>){
     let mut counts: HashMap<House, f64> = HashMap::new();
     for layout in db.layouts() {
         let price = city::get_price(&city, layout.houses()) as f64;
@@ -44,8 +44,8 @@ pub fn build_house_probabilities(city: &City, db: &LayoutDB, min_score: f64, max
     (index, houses.iter().map(|(house, _)| *house).collect())
 }
 
-pub fn populate_using_db(layout: &mut HouseLayout, mut rng: &mut StdRng, db: &LayoutDB, min_score: f64, max_score: f64, db_probability: f64) {
-    let (mut index, houses) = build_house_probabilities(&layout.city, &db, min_score, max_score);
+pub fn populate_using_db<TDB: LayoutDB>(layout: &mut HouseLayout, mut rng: &mut StdRng, db: &TDB, min_score: f64, max_score: f64, db_probability: f64) {
+    let (mut index, houses) = build_house_probabilities(&layout.city, db, min_score, max_score);
 
     loop {
         if rng.gen::<f64>() < db_probability {