Event Sourcing in Laravel: Aggregates & Projectors | Mohamed Said [ ![Mohamed Said](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MH.png) Mohamed Said Laravel Backend Engineer ](https://www.msaied.com) [ Home ](https://www.msaied.com) [ Projects ](https://www.msaied.com/projects) [ Articles ](https://www.msaied.com/articles) [ Certificates ](https://www.msaied.com/certificates) [ Contact ](https://www.msaied.com#contact-section) [ ](https://github.com/EG-Mohamed) [ Home ](https://www.msaied.com) [ Projects ](https://www.msaied.com/projects) [ Articles ](https://www.msaied.com/articles) [ Certificates ](https://www.msaied.com/certificates) [ Contact ](https://www.msaied.com#contact-section) [ home ](https://www.msaied.com) [ articles ](https://www.msaied.com/articles) Event Sourcing in Laravel: Aggregates, Projectors, and Rebuilding Read Models 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) ![Event Sourcing in Laravel: Aggregates, Projectors, and Rebuilding Read Models](https://cdn.msaied.com/647/586a0f822614fed8091917a895ebc502.png) #laravel #event-sourcing #ddd #eloquent #architecture Event Sourcing in Laravel: Aggregates, Projectors, and Rebuilding Read Models =============================================================================== 9 Sep 2026 3 min read ![Mohamed Said](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) Mohamed Said Table of contents 1. [ 01 Why Event Sourcing Is Worth the Complexity ](#why-event-sourcing-is-worth-the-complexity) 2. [ 02 Defining a Domain Event ](#defining-a-domain-event) 3. [ 03 The Aggregate Root ](#the-aggregate-root) 4. [ 04 The Event Store ](#the-event-store) 5. [ 05 Projectors: Building Read Models ](#projectors-building-read-models) 6. [ 06 Rebuilding Read Models Safely ](#rebuilding-read-models-safely) 7. [ 07 Packages Worth Knowing ](#packages-worth-knowing) 8. [ 08 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. Found this useful? [ ](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.msaied.com%2Farticles%2Fevent-sourcing-in-laravel-aggregates-projectors-and-rebuilding-read-models&text=Event+Sourcing+in+Laravel%3A+Aggregates%2C+Projectors%2C+and+Rebuilding+Read+Models) [ ](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.msaied.com%2Farticles%2Fevent-sourcing-in-laravel-aggregates-projectors-and-rebuilding-read-models) Frequently Asked Questions ---------------------------- 3 questions Q01 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. Q02 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. Q03 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. Continue reading More Articles --------------- [ View all ](https://www.msaied.com/articles) [ ![Read/Write Splitting and Sticky Reads in Laravel: A Production Guide](https://cdn.msaied.com/646/4155b1eed8a491a99c3dda6f7dddd80e.png) laravel database performance ### Read/Write Splitting and Sticky Reads in Laravel: A Production Guide Learn how Laravel's read/write connection splitting works under the hood, when sticky reads save you from repl... ![Mohamed Said](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) Mohamed Said 9 Sep 2026 3 min read Read ](https://www.msaied.com/articles/readwrite-splitting-and-sticky-reads-in-laravel-a-production-guide) [ ![Chunked Iteration, Lazy Collections, and Cursor Pagination at Scale in Laravel](https://cdn.msaied.com/645/3bcda55cd0d9e4e9b4be38c9b3d11ea4.png) laravel eloquent performance ### Chunked Iteration, Lazy Collections, and Cursor Pagination at Scale in Laravel Processing millions of Eloquent rows without exhausting memory requires the right tool for the job. Learn when... ![Mohamed Said](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) Mohamed Said 8 Sep 2026 4 min read Read ](https://www.msaied.com/articles/chunked-iteration-lazy-collections-and-cursor-pagination-at-scale-in-laravel) [ ![PostgreSQL JSONB in Laravel: Indexing, Querying, and Casting Without the Pain](https://cdn.msaied.com/643/656efe6f0c30b559bcdb27456edcc366.png) laravel postgresql eloquent ### PostgreSQL JSONB in Laravel: Indexing, Querying, and Casting Without the Pain JSONB columns unlock flexible schemas inside PostgreSQL, but misused they become slow blobs. Learn how to inde... ![Mohamed Said](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) Mohamed Said 8 Sep 2026 3 min read Read ](https://www.msaied.com/articles/postgresql-jsonb-in-laravel-indexing-querying-and-casting-without-the-pain-2) [ ![Mohamed Said](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MH.png) Mohamed Said Laravel Backend Engineer ](https://www.msaied.com)Senior Backend Engineer specializing in Laravel, scalable SaaS platforms, APIs, and cloud infrastructure. I build secure, high-performance web applications that help businesses grow. Explore - [Home](https://www.msaied.com) - [Projects](https://www.msaied.com/projects) - [Articles](https://www.msaied.com/articles) - [Certificates](https://www.msaied.com/certificates) - [Contact](https://www.msaied.com#contact-section) Connect - [ hello@msaied.com ](mailto:hello@msaied.com) - [ +20 109 461 9204 ](tel:+201094619204) © 2026 Mohamed Said. All rights reserved. [ ](https://github.com/EG-Mohamed) [ ](https://www.linkedin.com/in/msaiedm/) [ ](https://wa.me/201094619204) [ ](mailto:hello@msaied.com) [ ](https://drive.google.com/file/u/0/d/1MF20IPRJyzfy32mhEutjL5EpSls0w2Q8/view)