SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e6903754f9857f713092c2421317cebbf962dea971e1ce905c98745648514ca' 
  AND token = 'NejUjLO5yqcgUcagEFHq0QMHDSLVLMcTfOY+EIPwPzE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}