SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a264a480bf0d589b0b3882034677b60f8ff04386ffa9bbbefb7eefa94f94898' 
  AND token = 'Rs3CFohmWRa+zsTZTVB0bu8pgQ4iAXl3DhLlGnqkSHk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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