SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ff8d21bc3db187493c9639cc957a3d34501f19ebb57571a54eb2b0ece8a68ec' 
  AND token = '7DVrklCLftii5u8g/2DhzEv42Lkq8bFlpFz1Smzv/Ng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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