Kailash Nadh's FOSS contributions
Kailash Nadh’s FOSS contributions covers the free and open-source software (FOSS) projects created and maintained by Kailash Nadh, chief technology officer of Zerodha, India’s largest retail stockbroker. Nadh is one of the most prolific open-source contributors to emerge from the Indian technology industry and has released software used globally across multiple application domains, including email and newsletter infrastructure, application configuration, ephemeral communications, and general-purpose programming utilities. His FOSS work is conducted in a personal capacity alongside his professional role as CTO, though it reflects and reinforces the open-source engineering culture he has built at Zerodha.
A biographical account of Kailash Nadh as a person and technology leader is at Kailash Nadh.
Open-source philosophy
Kailash Nadh has articulated a philosophy of software development that runs consistently through his open-source contributions. Its key characteristics are minimalism, correctness, practical utility, and a minimal dependency surface. He has written about this philosophy at length on his personal blog at nadh.in.
He distinguishes between software that is simple because its problem domain is simple and software that achieves simplicity through careful design despite being applied to complex problems. The latter he regards as an achievement requiring sustained discipline. Open-source software that is simple in this second sense is more useful to other developers because it is easier to understand, audit, and modify. It is also more maintainable over time, since the original author or subsequent maintainers can understand the codebase even after a significant gap.
Nadh has written critically about open-source ecosystems characterised by large numbers of small, mutually dependent packages. He argues that this pattern creates fragility: any package in the dependency chain can be abandoned, broken, or compromised, and the consuming application inherits all of those risks. His preference for minimal dependencies is a direct response to this concern.
He has also written about the responsibilities of open-source maintainers: the commitment that publishing software creates to the community that depends on it, the ethical dimensions of deprecating widely used software without adequate notice or migration paths, and the difficulty of sustaining maintenance effort over long periods, particularly for individual contributors without institutional support.
Major projects
Listmonk
Listmonk is a self-hosted, high-performance newsletter and mailing list manager. It is Kailash Nadh’s most widely adopted open-source project and has attracted a global community of users and contributors.
Technical characteristics
Listmonk is written in Go on the server side and uses PostgreSQL as its sole database dependency. The choice of Go reflects Nadh’s preference for the language for networked server applications: Go compiles to a single self-contained binary, has strong concurrency support through goroutines, is fast, and has a standard library sufficient for a large proportion of server application requirements without importing external packages.
The choice of PostgreSQL, rather than a more lightweight embedded database, reflects Listmonk’s design for production use cases at scale. PostgreSQL supports the complex query and indexing requirements needed for subscriber management, campaign targeting with segmentation, and reporting at large subscriber volumes. Nadh has written about this choice, noting that PostgreSQL’s feature set and maturity make it a better fit than lighter databases for software that will be operated in production by parties who may not have deep database engineering expertise.
Listmonk’s architecture separates the management application (accessible through a browser-based admin interface) from the message-sending pipeline, allowing the sending infrastructure to be scaled independently from the management interface.
Features
Listmonk provides:
- Subscriber management with support for multiple lists, custom attributes, and segmentation
- Campaign creation, scheduling, and management with HTML and plain-text templates
- Transactional email capabilities for event-triggered messages
- A bounce handling system for managing undeliverable addresses
- Detailed campaign analytics including open rates, click rates, and unsubscribe rates
- A REST API for all management functions, enabling programmatic interaction and integration with other systems
- Support for multiple SMTP providers and bulk email sending services as message transports
Origins and release
Listmonk was developed to meet Zerodha’s own need for a newsletter management system. Zerodha communicates with its large client base through email for purposes including trade confirmations, account updates, product announcements, and educational content. Using commercial platforms like Mailchimp or Sendgrid for this volume of communication would have involved significant ongoing cost and would have placed client data in the hands of a third-party service provider.
Building Listmonk in-house solved both problems. When Nadh subsequently released it as open-source software, he made the solution available to any organisation with a similar need for high-volume email communication without dependence on commercial platforms.
Adoption and community
Listmonk has been adopted by publishers, non-governmental organisations, technology companies, and individual publishers globally. Its adoption is particularly notable among organisations that are philosophically committed to self-hosted and open-source infrastructure and among those whose data handling requirements make third-party newsletter platforms impractical (healthcare, legal, and government contexts, for example).
The project maintains its own documentation website at listmonk.app, which provides comprehensive installation, configuration, and usage guides. It has received coverage in international technology media including Linux Magazine and similar publications that cover self-hosted software.
Listmonk accepts community contributions and has a documented contribution process. Community members have contributed features, bug fixes, translations, and documentation improvements. Nadh maintains oversight of the project and reviews contributions to maintain code quality and design consistency.
Koanf
Koanf is a lightweight configuration management library for Go applications. It is available at github.com/knadh/koanf under an MIT licence and has been adopted in production Go applications across the industry.
Configuration management is a recurring need in Go applications: applications need to read settings from environment variables, command-line flags, configuration files, and potentially remote configuration systems, and they need to merge these sources with a defined precedence order. While Go’s standard library provides basic support for environment variables and flags, a library like Koanf is needed for the full configuration management use case.
Koanf’s design separates the configuration provider (the source of configuration values) from the parser (which interprets the format of the configuration data) and from the merge and access layer (which combines multiple sources and provides a unified access API). This separation allows new sources and formats to be added without modifying the core library.
The library supports JSON, YAML, TOML, dotenv, and other common configuration formats, and supports providers for environment variables, command-line flags, and remote systems. Its API allows configuration values to be accessed by dot-notated key paths, with type coercion handled automatically.
Koanf has been adopted in a range of Go projects including, most visibly, in the OpenTelemetry Collector, a widely used observability tool, which selected Koanf as its configuration library. This selection exposed Koanf to a large additional user base and contributed to its adoption.
Niltalk
Niltalk is a self-hosted ephemeral chat room server. It is designed for contexts where a temporary, anonymous, or privacy-preserving chat environment is needed: rooms can be created without registration, have a finite lifespan after which the room and all messages are deleted, and leave no persistent record. It is written in Go and uses WebSockets for real-time communication.
Niltalk addresses a specific use case that commercial messaging platforms do not serve well: the need for genuinely temporary conversations that disappear entirely after a defined period, with no account creation requirement and no data retention by the server operator. This makes it useful for contexts including customer support, temporary project coordination, and privacy-sensitive communication.
Database access tools
Nadh has developed tooling to simplify common patterns in accessing SQL databases from Go applications. These tools address recurring friction points in Go database programming including type-safe result scanning, query building, and connection pool management. The tools are used in Zerodha’s own database-intensive applications and released for broader use.
Language and text processing tools
Nadh’s GitHub profile includes several tools related to text processing, data format conversion, and language-related utilities. These reflect his interest in the intersection of language, structure, and software, a theme that also appears in his personal blog writing.
Historical and archived projects
Nadh’s GitHub profile (github.com/knadh) hosts a range of projects in various states of activity. Some are actively maintained production-grade tools (Listmonk, Koanf). Others are experimental utilities, archived projects reflecting earlier interests, or small tools developed for specific narrow purposes. The profile documents an engineering career spanning many years and application domains.
Contributions within Zerodha
Within Zerodha, Kailash Nadh has led the construction of Kite and Zerodha Console on an open-source stack, and has published the Kite Connect API which has enabled an ecosystem of third-party fintech applications. While these systems are not themselves open-source, the engineering practices, technology choices, and component libraries that underlie them reflect the same open-source philosophy as his personal FOSS work.
The Zerodha technology blog (zerodha.tech) publishes detailed accounts of engineering decisions, system designs, and technical approaches used within Zerodha. These posts contribute to the broader knowledge commons available to the Indian and global fintech engineering community, functioning as a form of knowledge contribution even when the code itself is not released.
Reception and significance
Kailash Nadh’s FOSS contributions are regarded within the Indian and international developer community as exemplary in their technical quality, maintenance commitment, and practical utility. Listmonk has been particularly noted as a reference implementation of self-hosted email infrastructure: well-documented, actively maintained, and technically sound.
Within India, his work has demonstrated that world-class open-source software is produced by Indian engineers at Indian companies, not solely as a by-product of employment at large multinational technology corporations. This has normative significance in a technology community where such visible examples from Indian companies have historically been less common.
The combination of his FOSS contributions and Nithin Kamath’s public advocacy for open-source adoption in Indian financial services has given Zerodha a distinctive position in the Indian fintech ecosystem: a company that argues for open-source infrastructure not only through words but through its own technology choices and its demonstrated ability to build competitive, high-quality financial technology on an entirely open-source foundation.
See also
References
- Kailash Nadh personal blog, nadh.in. Retrieved May 2026.
- GitHub profile, github.com/knadh. Retrieved May 2026.
- Listmonk project repository, github.com/knadh/listmonk. Retrieved May 2026.
- Listmonk documentation website, listmonk.app. Retrieved May 2026.
- Koanf project, github.com/knadh/koanf. Retrieved May 2026.
- Zerodha Technology Blog, zerodha.tech. Retrieved May 2026.
- The Economic Times, “Zerodha CTO’s open source tools are used across the world”, 2021.
- Linux Magazine, “Listmonk: A self-hosted mailing list manager”, 2021.
- OpenTelemetry Collector repository, use of Koanf as configuration library. github.com/open-telemetry/opentelemetry-collector. Retrieved May 2026.
- Inc42, “How Zerodha’s engineering culture is shaping Indian fintech”, 2020.