SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e7904d400a79a3cbd2eb309450c2ee6445f2aba7a167f147fca6aa123c028489' 
  AND token = 'kMZr/sOldAnLK+kGYfAF0HvvYSAF7czFCxtN5QbojA4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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