SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6bb6a10d3b494014747f26cef2419f3cffe9fd9a030a6c3da40a845911fd2f56' 
  AND token = 'Q0OMdWl+yL0GTlu197L+DyVFIZyt7WkCqKVoCJ3V9dQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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