SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ac343ffe264620f482459b43541207f0be87300d1ce883f83de757fe79feb3d' 
  AND token = 'U+ZM1e/z+TqV8Gom5QfVJ7XE3+P/MhpjfJ5SyUpWSLM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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