SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5708e81bd5843722a1fad74498b978bfcff0821e2859863e777c685358ea5f3' 
  AND token = 'NNc+D+nj+IlzYnJizsRuPp03QTgbJ6lB4HZj3lhETnw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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