SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b3d3121b6420eaf9d2d3f0d116c28add29de02ea73994ff71ea6317dce8e820' 
  AND token = '4NwSc0T4pyFE0oZuDRDIdnTsgcaPsdFZbQtMSKYetZ0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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