GraphQL adoption has grown massively among startups in the last few years, yet most API security guidance remains firmly REST-centric. This creates a dangerous blind spot as GraphQL introduces unique security challenges that traditional API protection strategies simply weren't designed to address.

There’s a steep learning curve for most engineers as concepts such as field-level authorisation aren’t found in REST APIs.

Why GraphQL security differs from REST

Unlike REST APIs with their fixed endpoints and predictable data returns, GraphQL provides a single endpoint where clients can request precisely the data they need. This flexibility is powerful, but it introduces novel attack vectors:

1. Query complexity exploitation - Attackers can craft nested queries that consume excessive server resources
2. Introspection vulnerabilities - GraphQL's self-documenting nature can reveal sensitive schema information
3. Resolver-specific weaknesses - Each resolver function presents a potential security boundary to manage

For non-technical founders, understanding these unique challenges is crucial when planning security investments and evaluating development priorities.

Technical implementation guide: Securing your GraphQL layer

Query complexity analysis

GraphQL allows clients to create deeply nested queries that can overload your database and create denial-of-service scenarios. Various libraries exist to implement query complexity analysis, such as graphql-query-complexity.

Authorisation in nested relationships

The biggest GraphQL security flaw that I most frequently see is improper authorisation in nested queries:

# Vulnerable query example
query {
	user(id: "current-user") {
		teams {
			projects {
				secretDocuments {
					# No authorization check here!
					content
				}
			}
		}
	}
}

Always implement authorisation at each resolver level, not just at the query entry point:

// Secure resolver pattern
const resolvers = {
	User: {
		teams: (parent, args, context) => {
			// Authorization check at the teams level
			if (!isAuthorizedForTeams(context.user, parent.id)) {
				throw new Error('Not authorized');
			}
			return getTeamsForUser(parent.id);
		}
	}
};

Performance-security balancing techniques

GraphQL's flexibility creates unique performance challenges that become security issues:

1. Implement field-level cost analysis - Assign weights to expensive fields
2. Use persisted queries - Whitelist approved queries to prevent query injection
3. Employ depth limiting - Restrict how deep queries can nest to prevent resource exhaustion
4. Consider resolver-specific rate limiting - Apply limits to particularly expensive operations

Business impact takeaways

GraphQL security failures typically manifest as:

• Unexpected server costs from query abuse
• Data leakage across tenant boundaries
• Slow performance leading to poor user experience
• Complete API unavailability during DoS attacks

Properly securing your GraphQL API early prevents these issues from becoming business crises as you scale.

Yours,
Søren

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