SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a4741153e58a11b1615c5a021987d259158984016a0f555be6aa7758124ce39' 
  AND token = 'nQFHAztQOiryd4JC+3cMMSQygqmZ/yg0jOZdvozXExs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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