SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6068740e8032c1b7cafdaecd69f5694016c680cbde552d086b33c3a0247da462' 
  AND token = 'VCp4Ui7XkPjwQvLIzwiwhu1o4vuzFOsWXFEa0/i29JI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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