inFilters

InFilters is a term used in software engineering to describe a family of components that operate on inbound data within a processing pipeline. They are designed to validate, sanitize, transform, or otherwise constrain input before it reaches downstream logic, storage, or business rules. In many architectures, inFilters are used in web servers, messaging systems, and data processing frameworks to enforce quality, security, and consistency at the edge of a system.

Design and behavior commonly center on modularity and composability. A typical inFilter implements a shared interface that consumes an input item and returns either a transformed item or signals an error. Filters may be stateless or retain light context such as configuration, counters, or lineage metadata. They are often configurable, order-sensitive, and support defined error-handling policies, including short-circuiting the pipeline or routing errors to a dedicated path.

Types of inFilters include validation (ensuring data meets criteria), sanitization (removing harmful or unwanted content), type conversion and normalization, security checks (authentication, authorization, token validation), rate limiting, de-duplication, and data enrichment with metadata. They can perform simple checks or complex transformations and are typically designed to be reusable across routes, topics, or streams.

In practice, inFilters are placed at the start of a processing chain, before business logic or downstream processors. They are often contrasted with outbound filters, which operate on data as it leaves a system. The term is commonly used across frameworks with slight variations in naming and scope. See also: filters, middleware, interceptor, and stream processing.