SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1c9a50f5afed41d46356e37fa134cc7604da7fda104bf76430fdc10b26299091' 
  AND token = 'dKSUc/6fB4SgBwVKolJ3Dr2oGx9WLUqU0J/X8XsSmz4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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