SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '51c34eb88b431a40032dd3730b94d6841e103e8432b9048d17c9bcd64c7f743b' 
  AND token = 'PdsXgK0c+kvMFeyrtQRoDnYoxZFzueJkBaIU3uKfd84=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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