diff --git a/src/aimedb/db.ts b/src/aimedb/db.ts
index dcb5365..c4b54a4 100644
--- a/src/aimedb/db.ts
+++ b/src/aimedb/db.ts
@@ -2,7 +2,7 @@ import sql from "sql-bricks-postgres";
 
 import { CardRepository, Repositories } from "./repo";
 import { AimeId, generateExtId } from "../model";
-import { Transaction, generateId } from "../sql";
+import { Transaction } from "../sql";
 
 class CardRepositoryImpl implements CardRepository {
   constructor(private readonly _txn: Transaction) {}
@@ -34,8 +34,8 @@ class CardRepositoryImpl implements CardRepository {
   }
 
   async register(luid: string, now: Date): Promise<AimeId> {
-    const playerId = generateId();
-    const cardId = generateId();
+    const playerId = this._txn.generateId();
+    const cardId = this._txn.generateId();
     const aimeId = generateExtId() as AimeId;
 
     const playerSql = sql.insert("aime_player", {
diff --git a/src/idz/db/backgrounds.ts b/src/idz/db/backgrounds.ts
index c48e77e..16d8866 100644
--- a/src/idz/db/backgrounds.ts
+++ b/src/idz/db/backgrounds.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { BackgroundCode } from "../model/base";
 import { Profile } from "../model/profile";
 import { FlagRepository } from "../repo";
-import { Id, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlBackgroundsRepository
   implements FlagRepository<BackgroundCode> {
@@ -38,7 +39,7 @@ export class SqlBackgroundsRepository
       }
 
       const saveSql = sql.insert("idz_background_unlock", {
-        id: generateId(),
+        id: this._txn.generateId(),
         profile_id: profileId,
         background_no: flag,
       });
diff --git a/src/idz/db/car.ts b/src/idz/db/car.ts
index fe8b856..3b8930a 100644
--- a/src/idz/db/car.ts
+++ b/src/idz/db/car.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { Car, CarSelector } from "../model/car";
 import { Profile } from "../model/profile";
 import { CarRepository } from "../repo";
-import { Id, Row, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Row, Transaction } from "../../sql";
 
 function _extractRow(row: Row): Car {
   return {
@@ -69,7 +70,7 @@ export class SqlCarRepository implements CarRepository {
   async saveCar(profileId: Id<Profile>, car: Car): Promise<void> {
     const saveSql = sql
       .insert("idz_car", {
-        id: generateId(),
+        id: this._txn.generateId(),
         profile_id: profileId,
         selector: car.selector,
         field_00: car.field_00,
diff --git a/src/idz/db/chara.ts b/src/idz/db/chara.ts
index a3ec589..ca4722f 100644
--- a/src/idz/db/chara.ts
+++ b/src/idz/db/chara.ts
@@ -4,7 +4,8 @@ import { BackgroundCode, TitleCode } from "../model/base";
 import { Chara, Gender } from "../model/chara";
 import { Profile } from "../model/profile";
 import { FacetRepository } from "../repo";
-import { Id, Row, Transaction } from "../../sql";
+import { Id } from "../../model";
+import { Row, Transaction } from "../../sql";
 
 export function _extractChara(row: Row): Chara {
   return {
diff --git a/src/idz/db/coursePlays.ts b/src/idz/db/coursePlays.ts
index c630d98..1cdab6c 100644
--- a/src/idz/db/coursePlays.ts
+++ b/src/idz/db/coursePlays.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { CourseNo } from "../model/base";
 import { Profile } from "../model/profile";
 import { CoursePlaysRepository } from "../repo";
-import { Id, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlCoursePlaysRepository implements CoursePlaysRepository {
   constructor(private readonly _txn: Transaction) {}
@@ -34,7 +35,7 @@ export class SqlCoursePlaysRepository implements CoursePlaysRepository {
     for (const [k, v] of plays) {
       const saveSql = sql
         .insert("idz_course_plays", {
-          id: generateId(),
+          id: this._txn.generateId(),
           profile_id: profileId,
           course_no: k,
           count: v,
diff --git a/src/idz/db/missions.ts b/src/idz/db/missions.ts
index e082c41..fea4182 100644
--- a/src/idz/db/missions.ts
+++ b/src/idz/db/missions.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { MissionGrid, MissionState } from "../model/mission";
 import { Profile } from "../model/profile";
 import { FacetRepository } from "../repo";
-import { Id, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlMissionsRepository implements FacetRepository<MissionState> {
   constructor(private readonly _txn: Transaction) {}
@@ -59,7 +60,7 @@ export class SqlMissionsRepository implements FacetRepository<MissionState> {
 
         const saveSql = sql
           .insert("idz_solo_mission_state", {
-            id: generateId(),
+            id: this._txn.generateId(),
             profile_id: profileId,
             grid_no: i,
             cell_no: j,
diff --git a/src/idz/db/profile.ts b/src/idz/db/profile.ts
index 0848638..ee409fb 100644
--- a/src/idz/db/profile.ts
+++ b/src/idz/db/profile.ts
@@ -2,8 +2,8 @@ import sql from "sql-bricks-postgres";
 
 import { Profile } from "../model/profile";
 import { ProfileRepository } from "../repo";
-import { AimeId } from "../../model";
-import { Id, Row, Transaction, generateId } from "../../sql";
+import { AimeId, Id } from "../../model";
+import { Row, Transaction } from "../../sql";
 
 export function _extractProfile(row: Row): Profile {
   return {
@@ -45,7 +45,7 @@ export class SqlProfileRepository implements ProfileRepository {
       return undefined;
     }
 
-    return BigInt(row.id) as Id<Profile>;
+    return row.id as Id<Profile>;
   }
 
   async load(id: Id<Profile>): Promise<Profile> {
@@ -91,7 +91,7 @@ export class SqlProfileRepository implements ProfileRepository {
       throw new Error("Aime ID not found");
     }
 
-    const id = generateId();
+    const id = this._txn.generateId<Profile>();
     const playerId = row.id;
 
     const createSql = sql.insert("idz_profile", {
@@ -109,6 +109,6 @@ export class SqlProfileRepository implements ProfileRepository {
 
     await this._txn.modify(createSql);
 
-    return id as Id<Profile>;
+    return id;
   }
 }
diff --git a/src/idz/db/settings.ts b/src/idz/db/settings.ts
index 7ef210e..bab0bff 100644
--- a/src/idz/db/settings.ts
+++ b/src/idz/db/settings.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { Settings } from "../model/settings";
 import { Profile } from "../model/profile";
 import { FacetRepository } from "../repo";
-import { Id, Transaction } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlSettingsRepository implements FacetRepository<Settings> {
   constructor(private readonly _txn: Transaction) {}
diff --git a/src/idz/db/story.ts b/src/idz/db/story.ts
index b585ac9..d799509 100644
--- a/src/idz/db/story.ts
+++ b/src/idz/db/story.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { Profile } from "../model/profile";
 import { Story, StoryRow, StoryCell } from "../model/story";
 import { FacetRepository } from "../repo";
-import { Id, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlStoryRepository implements FacetRepository<Story> {
   constructor(private readonly _txn: Transaction) {}
@@ -81,7 +82,7 @@ export class SqlStoryRepository implements FacetRepository<Story> {
 
         const cellSql = sql
           .insert("idz_story_cell_state", {
-            id: generateId(),
+            id: this._txn.generateId(),
             profile_id: profileId,
             row_no: i,
             col_no: j,
diff --git a/src/idz/db/team.ts b/src/idz/db/team.ts
index c579d71..368d83b 100644
--- a/src/idz/db/team.ts
+++ b/src/idz/db/team.ts
@@ -3,8 +3,8 @@ import sql from "sql-bricks-postgres";
 import { ExtId } from "../model/base";
 import { Team } from "../model/team";
 import { TeamSpec, TeamRepository } from "../repo";
-import { generateExtId } from "../../model";
-import { Id, Transaction, generateId } from "../../sql";
+import { Id, generateExtId } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlTeamRepository implements TeamRepository {
   constructor(private readonly _txn: Transaction) {}
@@ -21,7 +21,7 @@ export class SqlTeamRepository implements TeamRepository {
       throw new Error(`Team not found for ExtID ${extId}`);
     }
 
-    return BigInt(row.id) as Id<Team>;
+    return row.id as Id<Team>;
   }
 
   async load(id: Id<Team>): Promise<Team> {
@@ -57,7 +57,7 @@ export class SqlTeamRepository implements TeamRepository {
   }
 
   async create(team: TeamSpec): Promise<[Id<Team>, ExtId<Team>]> {
-    const id = generateId() as Id<Team>;
+    const id = this._txn.generateId<Team>();
     const extId = generateExtId() as ExtId<Team>;
 
     const createSql = sql.insert("idz_team", {
diff --git a/src/idz/db/teamAuto.ts b/src/idz/db/teamAuto.ts
index 3945da4..5aed74b 100644
--- a/src/idz/db/teamAuto.ts
+++ b/src/idz/db/teamAuto.ts
@@ -2,7 +2,8 @@ import sql from "sql-bricks-postgres";
 
 import { Team, TeamAuto } from "../model/team";
 import { TeamAutoRepository } from "../repo";
-import { Id, Transaction } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlTeamAutoRepository implements TeamAutoRepository {
   constructor(private readonly _txn: Transaction) {}
@@ -22,7 +23,7 @@ export class SqlTeamAutoRepository implements TeamAutoRepository {
           serialNo: parseInt(row.serial_no),
           nameIdx: parseInt(row.name_idx),
         },
-        BigInt(row.id) as Id<Team>,
+        row.id as Id<Team>,
       ]
     );
   }
diff --git a/src/idz/db/teamMember.ts b/src/idz/db/teamMember.ts
index 4bc8f92..45e2005 100644
--- a/src/idz/db/teamMember.ts
+++ b/src/idz/db/teamMember.ts
@@ -5,7 +5,8 @@ import { Team, TeamMember } from "../model/team";
 import { TeamMemberRepository } from "../repo";
 import { _extractProfile } from "./profile";
 import { _extractChara } from "./chara";
-import { Id, Transaction } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlTeamMemberRepository implements TeamMemberRepository {
   constructor(private readonly _txn: Transaction) {}
@@ -22,7 +23,7 @@ export class SqlTeamMemberRepository implements TeamMemberRepository {
       return undefined;
     }
 
-    return BigInt(row.team_id) as Id<Team>;
+    return row.team_id as Id<Team>;
   }
 
   async findLeader(teamId: Id<Team>): Promise<Id<Profile> | undefined> {
@@ -38,7 +39,7 @@ export class SqlTeamMemberRepository implements TeamMemberRepository {
       return undefined;
     }
 
-    return BigInt(row.id) as Id<Profile>;
+    return row.id as Id<Profile>;
   }
 
   async loadRoster(teamId: Id<Team>): Promise<TeamMember[]> {
@@ -65,7 +66,7 @@ export class SqlTeamMemberRepository implements TeamMemberRepository {
     profileId: Id<Profile>,
     timestamp: Date
   ): Promise<void> {
-    // Lock the team record to avoid race conditions. This way
+    // Lock the team record to avoid race conditions.
 
     const lockSql = sql
       .select("id")
diff --git a/src/idz/db/teamReservation.ts b/src/idz/db/teamReservation.ts
index 0e414b3..b52ad88 100644
--- a/src/idz/db/teamReservation.ts
+++ b/src/idz/db/teamReservation.ts
@@ -2,8 +2,8 @@ import sql from "sql-bricks-postgres";
 
 import { Team } from "../model/team";
 import { TeamReservationRepository } from "../repo";
-import { AimeId } from "../../model";
-import { Id, Transaction } from "../../sql";
+import { AimeId, Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlTeamReservationRepository
   implements TeamReservationRepository {
diff --git a/src/idz/db/tickets.ts b/src/idz/db/tickets.ts
index cf3aa65..616c0f4 100644
--- a/src/idz/db/tickets.ts
+++ b/src/idz/db/tickets.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { Profile } from "../model/profile";
 import { Tickets } from "../model/tickets";
 import { FacetRepository } from "../repo";
-import { Id, Transaction } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 // TODO free continue
 
diff --git a/src/idz/db/timeAttack.ts b/src/idz/db/timeAttack.ts
index b9e9f17..ae377cd 100644
--- a/src/idz/db/timeAttack.ts
+++ b/src/idz/db/timeAttack.ts
@@ -5,7 +5,8 @@ import { CarSelector } from "../model/car";
 import { Profile } from "../model/profile";
 import { TimeAttackScore } from "../model/timeAttack";
 import { TimeAttackRepository, TopTenResult } from "../repo";
-import { Id, Row, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Row, Transaction } from "../../sql";
 
 function _extractRow(row: Row): TimeAttackScore {
   return {
@@ -56,7 +57,7 @@ export class SqlTimeAttackRepository implements TimeAttackRepository {
 
   async save(profileId: Id<Profile>, score: TimeAttackScore): Promise<void> {
     const logSql = sql.insert("idz_ta_result", {
-      id: generateId(),
+      id: this._txn.generateId(),
       profile_id: profileId,
       route_no: score.routeNo,
       total_time: score.totalTime,
@@ -79,7 +80,7 @@ export class SqlTimeAttackRepository implements TimeAttackRepository {
 
     if (row === undefined) {
       const insertSql = sql.insert("idz_ta_best", {
-        id: generateId(),
+        id: this._txn.generateId(),
         profile_id: profileId,
         route_no: score.routeNo,
         total_time: score.totalTime,
diff --git a/src/idz/db/titles.ts b/src/idz/db/titles.ts
index 5bc9550..7a79071 100644
--- a/src/idz/db/titles.ts
+++ b/src/idz/db/titles.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { TitleCode } from "../model/base";
 import { Profile } from "../model/profile";
 import { FlagRepository } from "../repo";
-import { Id, Transaction, generateId } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlTitlesRepository implements FlagRepository<TitleCode> {
   constructor(private readonly _txn: Transaction) {}
@@ -33,7 +34,7 @@ export class SqlTitlesRepository implements FlagRepository<TitleCode> {
       }
 
       const saveSql = sql.insert("idz_title_unlock", {
-        id: generateId(),
+        id: this._txn.generateId(),
         profile_id: profileId,
         title_no: flag,
       });
diff --git a/src/idz/db/unlocks.ts b/src/idz/db/unlocks.ts
index d3e30f2..9e7f66c 100644
--- a/src/idz/db/unlocks.ts
+++ b/src/idz/db/unlocks.ts
@@ -3,7 +3,8 @@ import sql from "sql-bricks-postgres";
 import { Profile } from "../model/profile";
 import { Unlocks } from "../model/unlocks";
 import { FacetRepository } from "../repo";
-import { Id, Transaction } from "../../sql";
+import { Id } from "../../model";
+import { Transaction } from "../../sql";
 
 export class SqlUnlocksRepository implements FacetRepository<Unlocks> {
   constructor(private readonly _txn: Transaction) {}
diff --git a/src/idz/handler/_team.ts b/src/idz/handler/_team.ts
index 07685e1..e74a64e 100644
--- a/src/idz/handler/_team.ts
+++ b/src/idz/handler/_team.ts
@@ -1,6 +1,6 @@
 import { Team } from "../model/team";
 import { Repositories } from "../repo";
-import { Id } from "../../sql";
+import { Id } from "../../model";
 
 // Bleh. This factorization is kind of messy.
 
diff --git a/src/idz/repo.ts b/src/idz/repo.ts
index d1577b2..213a6a5 100644
--- a/src/idz/repo.ts
+++ b/src/idz/repo.ts
@@ -1,10 +1,7 @@
 import { Subtract } from "utility-types";
 
 import * as Model from "./model";
-import { AimeId } from "../model";
-import { Id } from "../sql";
-
-// Id<> is a layer break here... need to find a better way to deal with this.
+import { AimeId, Id } from "../model";
 
 export type TeamSpec = Subtract<
   Model.Team,
diff --git a/src/model.ts b/src/model.ts
index 98ddf2a..4484e1f 100644
--- a/src/model.ts
+++ b/src/model.ts
@@ -1,5 +1,22 @@
 import { randomBytes } from "crypto";
 
+/**
+ * An internal database id.
+ *
+ * We don't have any say over the protocols that we are implementing, and we
+ * would also like our internal data store to adhere to a consistent set of
+ * design principles. This type defines a fully opaque primary key data type
+ * for database records which should not be exposed to external clients under
+ * normal circumstances. Clients outside the SQL DB (or other persistent data
+ * storage) driver should make no assumptions about its structure or actual
+ * underlying data type.
+ *
+ * Database entities presented to external clients must be identified using
+ * alternative external identifiers in formats that are acceptable to those
+ * external systems.
+ */
+export type Id<T> = string & { __type: T };
+
 export type AimeId = number & { __aimeId: null };
 
 /** Generate a random 32-bit ID for use in external protocol messages */
diff --git a/src/sql/api.ts b/src/sql/api.ts
index e0b3dfe..bc540e1 100644
--- a/src/sql/api.ts
+++ b/src/sql/api.ts
@@ -1,12 +1,23 @@
 import * as sql from "sql-bricks-postgres";
 
-export type Id<T> = bigint & { __id: T };
+import { Id } from "../model";
 
 export interface Row {
   [key: string]: string;
 }
 
 export interface Transaction {
+  /**
+   * Generate a new random primary key.
+   *
+   * On SQLite this is a random 63-bit integer (the high bit is always zero
+   * so that all IDs are positive, mostly for aesthetic reasons although this
+   * may also usefully reserve a namespace for automated testing).
+   *
+   * On Postgres this might generate UUIDv4s instead.
+   */
+  generateId<T>(): Id<T>;
+
   modify(stmt: sql.Statement): Promise<void>;
 
   fetchRow(stmt: sql.SelectStatement): Promise<Row | undefined>;
diff --git a/src/sql/index.ts b/src/sql/index.ts
index 5beb3b9..d9c9c91 100644
--- a/src/sql/index.ts
+++ b/src/sql/index.ts
@@ -1,3 +1,2 @@
 export * from "./api";
 export * from "./sqlite";
-export * from "./util";
diff --git a/src/sql/sqlite.ts b/src/sql/sqlite.ts
index d19b78b..5cab2b9 100644
--- a/src/sql/sqlite.ts
+++ b/src/sql/sqlite.ts
@@ -1,7 +1,9 @@
 import Database from "better-sqlite3";
+import { randomBytes } from "crypto";
 import * as sql from "sql-bricks-postgres";
 
 import { DataSource, Row, Transaction } from "./api";
+import { Id } from "../model";
 
 type MixedRow = {
   [key: string]: any;
@@ -52,6 +54,17 @@ function _postprocess(obj: MixedRow): Row {
 class SqliteTransaction implements Transaction {
   constructor(private readonly _db: Database.Database) {}
 
+  generateId<T>(): Id<T> {
+    const buf = randomBytes(8);
+
+    buf[0] &= 0x7f; // Force number to be non-negative
+
+    const val = buf.readBigUInt64BE(0);
+    const str = val.toString();
+
+    return str as Id<T>;
+  }
+
   modify(stmt: sql.Statement): Promise<void> {
     const params = _preprocess(stmt);
 
diff --git a/src/sql/util.ts b/src/sql/util.ts
deleted file mode 100644
index 45c01bf..0000000
--- a/src/sql/util.ts
+++ /dev/null
@@ -1,14 +0,0 @@
-import { randomBytes } from "crypto";
-
-export function generateId(): bigint {
-  const buf = randomBytes(8);
-
-  buf[0] &= 0x7f; // Force number to be non-negative
-
-  // Let's not depend on Node v12 for the sake of 3 LoC just yet.
-
-  const hi = buf.readUInt32BE(0);
-  const lo = buf.readUInt32BE(4);
-
-  return (BigInt(hi) << 32n) | BigInt(lo);
-}