SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f68a318e8cd4383e223fa90cae289376af0fee5b3840475a288b313d647dfc6' 
  AND token = 'Nn8VbLSqaPTWf2yz+aF5LYKfN8k67jChI9j8qMa7bas=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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