SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8bf753672e7de7b102b9a44bf3e0462f24cdce98923ac1d835f1463c71bf684' 
  AND token = '4IAcobwTxBAuqXKHmLVxwSt2RXiEvUJb5muwprLgxtk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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