SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '721fc417219ad76d54cef3b338c2e5c8a63b5110cce022b9f963342291779cb8' 
  AND token = '8vZdl6yd6uotn88kf462EnSlvwyJWYh1UDgFnvZgo48=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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