SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '34577317552b7539743ad9ed9010ccfce088b91f2f755a165835295d4f3add20' 
  AND token = 'UxSR56NXU3HiHVII0QL1cACkHvwTan4kH+G56FIyv0c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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