Senior Software Engineer, Rules Engine & Parsing

Our product runs on rules. Analysts write them as short expressions like 'amount > 1000 && (region == "US" || vip)', and we evaluate each one against every record that comes through. We're hiring a senior engineer to own the engine behind them: a lexer, a parser, and an evaluator, written in plain Java with no parsing libraries.

What you'll do:

• Get operator precedence and associativity right across arithmetic, comparison, boolean, and unary operators, plus parentheses, variables, and a handful of built-in functions
• Tokenize correctly, including multi-character operators and syntax errors that point at the right position
• Evaluate expressions and return clear, typed errors for what goes wrong: unknown variables, divide-by-zero, type mismatches, and wrong argument counts
• Keep the whole pipeline predictable and well tested

What we're looking for:

• Strong Java and hands-on parsing experience: tokenizing, building an AST, and handling precedence
• Good instincts for expression evaluation and error handling
• The judgment to hand-write focused code instead of reaching for a parser generator

Nice to have:

Built an interpreter or rules engine before, and familiar with recursive-descent or precedence-climbing parsing