SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ccb8418dc0a8bff1f1ee44d22f5e8d45df4983f7888bc5ce4c83316e7344f705' 
  AND token = '6r8/DgMQ0XWBhROIDxSIqvsRYKkrVmuFmfeYZdgwOHE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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