SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50fea1b49a3cfdfbcd5543f9da5dad60377edd83d800cbd6761730c90547b858' 
  AND token = 'qjgKbcN3VpmQPbun6jzu+bYIz0qEnGcYTJxevygt3xQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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