SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '336df7cb15cdb9ad23943e425ed04f87184131e41a1e66d1569dbb9361dc3039' 
  AND token = 'xUePhyAiBzgfmwXi+UTyTrtWQretGa4JqFbILeGXKlw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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