SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cefbb4972dde73efedba01c413f0482975c9094596f52b9a3f808c631e4e38fd' 
  AND token = 'jsjS6KBlohOnhYAWkysj9tNl8fAzl1aIAHIrijALCiU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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