SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '708c2106bcb8587d2ad348d1bd2d320180e85cd2e03891635e633abcbb3278e3' 
  AND token = 'WiUr0HWN7582HnINabWjP+A922B+LX2xOQvLycu9SUc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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