diff --git a/src/db-copy.cpp b/src/db-copy.cpp
index bb3d97cf3..261bb95ed 100644
--- a/src/db-copy.cpp
+++ b/src/db-copy.cpp
@@ -15,7 +15,8 @@
 #include "pgsql.hpp"
 
 void db_deleter_by_id_t::delete_rows(std::string const &table,
-                                     std::string const &column, pg_conn_t *conn)
+                                     std::string const &column,
+                                     pg_conn_t const &db_connection)
 {
     fmt::memory_buffer sql;
     // Each deletable contributes an OSM ID and a comma. The highest node ID
@@ -32,12 +33,12 @@ void db_deleter_by_id_t::delete_rows(std::string const &table,
     sql[sql.size() - 1] = ')';
 
     sql.push_back('\0');
-    conn->exec(sql.data());
+    db_connection.exec(sql.data());
 }
 
 void db_deleter_by_type_and_id_t::delete_rows(std::string const &table,
                                               std::string const &column,
-                                              pg_conn_t *conn)
+                                              pg_conn_t const &db_connection)
 {
     assert(!m_deletables.empty());
 
@@ -78,7 +79,7 @@ void db_deleter_by_type_and_id_t::delete_rows(std::string const &table,
     }
 
     sql.push_back('\0');
-    conn->exec(sql.data());
+    db_connection.exec(sql.data());
 }
 
 db_copy_thread_t::db_copy_thread_t(connection_params_t const &connection_params)
@@ -182,7 +183,7 @@ void db_copy_thread_t::thread_t::write_to_db(db_cmd_copy_t *buffer)
         finish_copy();
     }
 
-    buffer->delete_data(m_db_connection.get());
+    buffer->delete_data(*m_db_connection);
 
     if (!m_inflight) {
         start_copy(buffer->target);
diff --git a/src/db-copy.hpp b/src/db-copy.hpp
index b3b710e8a..a297d0f15 100644
--- a/src/db-copy.hpp
+++ b/src/db-copy.hpp
@@ -85,7 +85,7 @@ class db_deleter_by_id_t
     void add(osmid_t osm_id) { m_deletables.push_back(osm_id); }
 
     void delete_rows(std::string const &table, std::string const &column,
-                     pg_conn_t *conn);
+                     pg_conn_t const &db_connection);
 
     bool is_full() const noexcept { return m_deletables.size() > Max_entries; }
 
@@ -126,7 +126,7 @@ class db_deleter_by_type_and_id_t
     }
 
     void delete_rows(std::string const &table, std::string const &column,
-                     pg_conn_t *conn);
+                     pg_conn_t const &db_connection);
 
     bool is_full() const noexcept { return m_deletables.size() > Max_entries; }
 
@@ -183,7 +183,7 @@ struct db_cmd_copy_t : public db_cmd_t
     std::string buffer;
 
     virtual bool has_deletables() const noexcept = 0;
-    virtual void delete_data(pg_conn_t *conn) = 0;
+    virtual void delete_data(pg_conn_t const &db_connection) = 0;
 
     explicit db_cmd_copy_t(std::shared_ptr<db_target_descr_t> t)
     : db_cmd_t(db_cmd_t::Cmd_copy), target(std::move(t))
@@ -209,12 +209,12 @@ class db_cmd_copy_delete_t : public db_cmd_copy_t
         return m_deleter.has_data();
     }
 
-    void delete_data(pg_conn_t *conn) override
+    void delete_data(pg_conn_t const &db_connection) override
     {
         if (m_deleter.has_data()) {
             m_deleter.delete_rows(
                 qualified_name(target->schema(), target->name()), target->id(),
-                conn);
+                db_connection);
         }
     }
 
diff --git a/src/expire-output.cpp b/src/expire-output.cpp
index cc4f90465..68d2ac372 100644
--- a/src/expire-output.cpp
+++ b/src/expire-output.cpp
@@ -58,38 +58,38 @@ std::size_t expire_output_t::output_tiles_to_table(
 {
     auto const qn = qualified_name(m_schema, m_table);
 
-    pg_conn_t connection{connection_params, "expire"};
+    pg_conn_t const db_connection{connection_params, "expire"};
 
-    auto const result = connection.exec("SELECT * FROM {} LIMIT 1", qn);
+    auto const result = db_connection.exec("SELECT * FROM {} LIMIT 1", qn);
 
     if (result.num_fields() == 3) {
         // old format with fields: zoom, x, y
-        connection.exec("PREPARE insert_tiles(int4, int4, int4) AS"
-                        " INSERT INTO {} (zoom, x, y) VALUES ($1, $2, $3)"
-                        " ON CONFLICT DO NOTHING",
-                        qn);
+        db_connection.exec("PREPARE insert_tiles(int4, int4, int4) AS"
+                           " INSERT INTO {} (zoom, x, y) VALUES ($1, $2, $3)"
+                           " ON CONFLICT DO NOTHING",
+                           qn);
     } else {
         // new format with fields: zoom, x, y, first, last
-        connection.exec("PREPARE insert_tiles(int4, int4, int4) AS"
-                        " INSERT INTO {} (zoom, x, y) VALUES ($1, $2, $3)"
-                        " ON CONFLICT (zoom, x, y)"
-                        " DO UPDATE SET last = CURRENT_TIMESTAMP(0)",
-                        qn);
+        db_connection.exec("PREPARE insert_tiles(int4, int4, int4) AS"
+                           " INSERT INTO {} (zoom, x, y) VALUES ($1, $2, $3)"
+                           " ON CONFLICT (zoom, x, y)"
+                           " DO UPDATE SET last = CURRENT_TIMESTAMP(0)",
+                           qn);
     }
 
     auto const count = for_each_tile(
         tiles_at_maxzoom, m_minzoom, m_maxzoom, [&](tile_t const &tile) {
-            connection.exec_prepared("insert_tiles", tile.zoom(), tile.x(),
-                                     tile.y());
+            db_connection.exec_prepared("insert_tiles", tile.zoom(), tile.x(),
+                                        tile.y());
         });
 
     return count;
 }
 
-void expire_output_t::create_output_table(pg_conn_t const &connection) const
+void expire_output_t::create_output_table(pg_conn_t const &db_connection) const
 {
     auto const qn = qualified_name(m_schema, m_table);
-    connection.exec(
+    db_connection.exec(
         "CREATE TABLE IF NOT EXISTS {} ("
         " zoom int4 NOT NULL,"
         " x int4 NOT NULL,"
diff --git a/src/expire-output.hpp b/src/expire-output.hpp
index fc4dba4ad..1c9821617 100644
--- a/src/expire-output.hpp
+++ b/src/expire-output.hpp
@@ -76,7 +76,7 @@ class expire_output_t
     /**
      * Create table for tiles.
      */
-    void create_output_table(pg_conn_t const &connection) const;
+    void create_output_table(pg_conn_t const &db_connection) const;
 
 private:
     /// The filename (if any) for output