SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6e4639d46fa1c6a564eeffc53d741965f5efcd3a992a0a32312d260a80fe493' 
  AND token = '5dZl/eyqBwY9G1xNRJb6XJSt0QDXQp/09l2B8cpTp9Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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