SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1d343b3ca468b6cd221e13bcabe53fbad6f966e6813c8abb5438417b0933a785' 
  AND token = 'B3vQhhwmz0PSyt5r0PLCVKhLbN6xZpPkwh5jGO7ZL0Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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