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Java Developer sought for developing Open Source ElasticSearch plug-ins

Java Developer sought for developing Open Source ElasticSearch plug-ins

We are searching for a Java developer for writing a series of open source plug-ins for ElasticSearch and interact with our research team.



Skills required:

  1. Java development experience of 3+ years.
  2. Familiarity with search engines such as Apache SOLR or ElasticSearch, a significant plus.
  3. Experience in a research environment, a plus.


  • Our research team has been awarded a prestigious grant from the Data Transparency Lab. The grant is for "FA*IR: A tool for fair rankings in search," which is a new ranking method proposed by our team to avoid discrimination by gender, race, or other protected characteristics. The team includes researchers from Universitat Pompeu Fabra in Barcelona (Dr. C. Castillo, Dr. R. Baeza-Yates), TU Berlin (Mrs. M. Zehlike), NTENT Hispania (Dr. R. Baeza-Yates, Dr. Sara Hajian), and ISI Torino (Dr. F. Bonchi).
  • Within this grant, we are searching for a Java developer for writing a series of plug-ins for ElasticSearch (or alternatively, for SOLR) and interact with our research team. The plug-ins will implement re-ranking strategies for queries in which the documents correspond to descriptions of people (e.g., resumes). We have two groups of plug-ins that will implement algorithms parametrized by a configuration file.
    1. The first group of plug-ins will implement a series of criteria that must be fulfilled by every response to a query (e.g., that for every query, the resulting list of documents must contain a minimum proportion of women in the first positions). These criteria will be based on the paper by Zehlike et al. 2017 at CIKM 2017.
    2. The second group of plug-ins will implement a learning-to-rank re-ranking strategy. They will receive a set of training documents, in which the ranking has been manually established, and will learn how to rank new, unseen documents, based on these training documents and criteria of fairness to be established during the research.
  • In both cases, the plug-ins should not be detrimental to the performance of the search engine, i.e., at most a small extra latency can be incurred. We expect that efficient fair ranking plug-ins will be a significant contribution to ElasticSearch, and given that they will be released as Open Source software, they will have significant impact in the huge user base of ElasticSearch.


  • The developer will meet a team member once per week to report progress. At least half of the meetings must be in person, the other half can be remote. The team is based in Barcelona and Berlin, so the developer must be able to attend the in-person meetings in one of these cities at his/her own expense. A developer based in the Barcelona or Berlin area will be preferred.


  • The project will start in February or March and end in July 2018 (5-6 months). The first group of plug-ins can be implemented immediately. The second group can be implemented from April'18, as the research of the research team progresses.
  • Bids will be reviewed from February 1st, 2018 and reviewed until a suitable developer is found.

What we offer:

  • Interaction with a team of international researchers.
  • Working on an application for social good, to mitigate or remove discrimination.
  • Contributing to Open Source software.

How to bid:

  • Questions may be asked by e-mail to Carlos Castillo [email protected]; please include the word "FA*IR" in the subject.
  • To bid, use this form.
    1. Include your CV with 2-3 recent relevant projects and your role on them
    2. Include your bid consisting of a work plan consisting of 2-3 phases for the project, the estimated number of work hours and timeline for each phase, and the cost of each phase. After the completion of each phase, a payment will be issued.
  • Contracting will be done directly between the developer and the Technical University of Berlin.

Salary and expenses: the total project cost should not exceed 24,000€ -- this is before any applicable taxes or deductions are applied.

To bid, use this form »