SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '171f7815e698f1938096bb4b4052db89a34f8568adea187643b4eb68a9ae9026' 
  AND token = '5qomxxK2aMel8unqnJXA1CJX56EghjSI5W+GfDY1+YU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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