SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fb0feb13267bb981552b001d6dff1797cd993ef64a66eec015368bc2019a51b9' 
  AND token = 'OJsBUDgyv6veb0RNlFt+fXOhGOBPcI7YyJCrhR0+KoE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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