SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c4cae2c21c42eaa7feeb1f009351420e865200c9c210b7d1b3b08469347bd3f' 
  AND token = '+V4BgHWDs1XHnp/bhG9QDXNjOJMpSWao/xiRpuBTjyQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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