SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '223648aabeb982c4a1e9f1cdc9f365a637bf1de88e69cd4be24ee1ff28bb808e' 
  AND token = '503u7YAgEiOJHFFNRXlOC8nzV+PDyZk8Gh6Lau6hIWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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