SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '710791fb207b303960e7779c39a40d03c24b6ba8c26615992b4591311a284b88' 
  AND token = 'jvRQ4nWBlLE9kzzGUD2P25CJAZYYejNi0KW4BmZsiuA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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