Event Sourcing in Laravel: Aggregates & Projectors | Mohamed Said [Skip to content](#main) [ ![](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MH.png) Mohamed SaidLaravel Backend Engineer ](https://www.msaied.com/public) - [Home](https://www.msaied.com/public) - [Projects](https://www.msaied.com/public/projects) - [Articles](https://www.msaied.com/public/articles) - [Certificates](https://www.msaied.com/public/certificates) - [About](https://www.msaied.com/public#about) [ Contact](https://www.msaied.com/public#contact) Menu Menu ---- Close - [HomeStart here](https://www.msaied.com/public) - [ProjectsCase studies](https://www.msaied.com/public/projects) - [ArticlesEngineering notes](https://www.msaied.com/public/articles) - [CertificatesCredentials](https://www.msaied.com/public/certificates) - [AboutHow I work](https://www.msaied.com/public#about) - [ContactGet in touch](https://www.msaied.com/public#contact) [Start a conversation](https://www.msaied.com/public#contact) [WhatsApp](https://wa.me/201094619204) [Email](mailto:hello@msaied.com) 1. [Home](https://www.msaied.com/public) 2. / 3. [Articles](https://www.msaied.com/public/articles) 4. / 5. Event Sourcing in Laravel: Aggregates, Projectors, and Rebuilding Read Models Event Sourcing in Laravel: Aggregates, Projectors, and Rebuilding Read Models ============================================================================== A practical walkthrough of event sourcing in Laravel — defining aggregates, persisting domain events, building projectors, and safely rebuilding read models without downtime. ![](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) [Mohamed Said](https://www.msaied.com/public#person) Published 9 Sep 2026 · Updated 9 Sep 2026 · 3 min read ShareCopy linkCopied ![Event Sourcing in Laravel: Aggregates, Projectors, and Rebuilding Read Models](https://cdn.msaied.com/647/586a0f822614fed8091917a895ebc502.png) On this page +1. [Why Event Sourcing Is Worth the Complexity](#why-event-sourcing-is-worth-the-complexity) 2. [Defining a Domain Event](#defining-a-domain-event) 3. [The Aggregate Root](#the-aggregate-root) 4. [The Event Store](#the-event-store) 5. [Projectors: Building Read Models](#projectors-building-read-models) 6. [Rebuilding Read Models Safely](#rebuilding-read-models-safely) 7. [Packages Worth Knowing](#packages-worth-knowing) 8. [Key Takeaways](#key-takeaways) Why Event Sourcing Is Worth the Complexity ------------------------------------------ Event sourcing replaces mutable row updates with an append-only log of domain events. Your database never forgets what happened — it only records *that* it happened. The current state is a projection of that history. For audit-heavy, financially sensitive, or highly collaborative domains, this is not over-engineering; it is the correct model. This article focuses on the mechanics: aggregates, the event store, projectors, and the rebuild story. --- Defining a Domain Event ----------------------- Domain events are plain, immutable value objects. Use PHP 8.2+ readonly classes: ```php final readonly class MoneyDeposited { public function __construct( public string $accountId, public int $amountCents, public string $currency, public \DateTimeImmutable $occurredAt, ) {} } ``` No Eloquent, no infrastructure concerns — just data. --- The Aggregate Root ------------------ An aggregate root applies events to itself and records them for persistence. It never touches the database directly. ```php final class BankAccount { private int $balanceCents = 0; private array $recordedEvents = []; public static function open(string $id, int $initialDeposit): self { $account = new self($id); $account->apply(new MoneyDeposited($id, $initialDeposit, 'USD', new \DateTimeImmutable())); return $account; } public function deposit(int $amountCents): void { if ($amountCents apply(new MoneyDeposited($this->id, $amountCents, 'USD', new \DateTimeImmutable())); } private function apply(object $event): void { $this->recordedEvents[] = $event; $this->when($event); } private function when(object $event): void { match (true) { $event instanceof MoneyDeposited => $this->balanceCents += $event->amountCents, default => null, }; } public function releaseEvents(): array { $events = $this->recordedEvents; $this->recordedEvents = []; return $events; } } ``` The `when()` method is the state machine. It is also used during reconstitution — replaying stored events rebuilds the aggregate without hitting any read model. --- The Event Store --------------- Store events as serialised JSON rows, never update them: ```php Schema::create('stored_events', function (Blueprint $table) { $table->id(); $table->string('aggregate_id')->index(); $table->string('aggregate_type'); $table->string('event_class'); $table->jsonb('payload'); $table->unsignedBigInteger('version'); $table->timestamp('created_at'); $table->unique(['aggregate_id', 'version']); // optimistic concurrency }); ``` The unique constraint on `(aggregate_id, version)` is your optimistic concurrency guard — two concurrent writes for the same version will produce a database error, not silent data corruption. --- Projectors: Building Read Models -------------------------------- A projector listens to stored events and maintains a denormalised read model: ```php final class AccountBalanceProjector { public function onMoneyDeposited(MoneyDeposited $event): void { AccountBalance::updateOrCreate( ['account_id' => $event->accountId], ['balance_cents' => \DB::raw("balance_cents + {$event->amountCents}")], ); } } ``` Projectors are side-effect machines. Keep them thin — no business logic, no conditionals beyond routing. --- Rebuilding Read Models Safely ----------------------------- This is the killer feature. When your read model schema changes, replay all events: ```php final class RebuildAccountBalances extends Command { protected $signature = 'projections:rebuild-balances'; public function handle(EventStore $store, AccountBalanceProjector $projector): void { AccountBalance::truncate(); $store->allForType(BankAccount::class) ->lazy() ->each(function (StoredEvent $stored) use ($projector) { $event = $stored->toEvent(); if ($event instanceof MoneyDeposited) { $projector->onMoneyDeposited($event); } }); $this->info('Rebuild complete.'); } } ``` For zero-downtime rebuilds, write to a shadow table, verify, then swap with a transaction and a view rename. --- Packages Worth Knowing ---------------------- `spatie/laravel-event-sourcing` provides a solid, production-tested foundation — aggregate roots, projectors, reactors, and a stored events table out of the box. Roll your own only if you have constraints it cannot satisfy. --- Key Takeaways ------------- - **Aggregates own business rules**; they never touch persistence directly. - **Events are immutable facts** — readonly classes enforce this at the language level. - **Optimistic concurrency** via a unique `(aggregate_id, version)` index prevents split-brain writes. - **Projectors are disposable** — the event log is the truth; read models are derived and rebuildable. - **Lazy collection replay** keeps memory flat during large rebuilds. - Shadow-table rebuilds enable schema migrations without downtime. - [laravel](https://www.msaied.com/public/articles?search=laravel) - [event-sourcing](https://www.msaied.com/public/articles?search=event-sourcing) - [ddd](https://www.msaied.com/public/articles?search=ddd) - [eloquent](https://www.msaied.com/public/articles?search=eloquent) - [architecture](https://www.msaied.com/public/articles?search=architecture) Frequently asked questions --------------------------- Do I need event sourcing for every Laravel application?No. Event sourcing adds real complexity — serialisation, replay logic, projector maintenance. It pays off in domains where audit history, temporal queries, or complex state machines are core requirements. For a standard CRUD app, it is overkill. How do I handle aggregate reconstitution from the event store?Load all stored events for a given aggregate ID ordered by version, then replay them through the aggregate's `when()` method without calling `apply()` (which would re-record them). The final in-memory state is the current aggregate state. What happens if a projector fails mid-rebuild?Track the last successfully processed event ID in a checkpoint table. On retry, resume from that checkpoint rather than replaying from the beginning. This makes rebuilds idempotent and safe to interrupt. ![Mohamed Said](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp)About the author ---------------- [Mohamed Said](https://www.msaied.com/public#person)Senior Backend Engineer specializing in Laravel, scalable SaaS platforms, APIs, and cloud infrastructure. I build secure, high-performance web applications that help businesses grow. [About](https://www.msaied.com/public#about) [GitHub ↗](https://github.com/EG-Mohamed) [LinkedIn ↗](https://www.linkedin.com/in/msaiedm/) [WhatsApp ↗](https://wa.me/201094619204) [Email Address ↗](mailto:hello@msaied.com) [My CV ↗](https://drive.google.com/file/u/0/d/1MF20IPRJyzfy32mhEutjL5EpSls0w2Q8/view) [Previous articleQueue totalSize() and JobInterrupted Event in Laravel 13.31](https://www.msaied.com/public/articles/queue-totalsize-and-jobinterrupted-event-in-laravel-1331) [Next articlePostgreSQL Window Functions in Laravel: Ranking, Running Totals, and Gap Detection](https://www.msaied.com/public/articles/postgresql-window-functions-in-laravel-ranking-running-totals-and-gap-detection-2) On this page ------------- 1. [Why Event Sourcing Is Worth the Complexity](#why-event-sourcing-is-worth-the-complexity) 2. [Defining a Domain Event](#defining-a-domain-event) 3. [The Aggregate Root](#the-aggregate-root) 4. [The Event Store](#the-event-store) 5. [Projectors: Building Read Models](#projectors-building-read-models) 6. [Rebuilding Read Models Safely](#rebuilding-read-models-safely) 7. [Packages Worth Knowing](#packages-worth-knowing) 8. [Key Takeaways](#key-takeaways) ### Have a technical challenge? Tell me what you’re building. I reply within two working days. 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