SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20eb5c230d8bf99b00725cc1d8e847aee2f9cdf4c7bc96d1837b8f77bd7e1e21' 
  AND token = 'HjtDqoEYLX9rVDRhQ/+lHjtDan08c9DPLJHKVCW91+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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