SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d703789f305308e1058eb3980ed75e1ba144c178efc846000bf8e16544dba4' 
  AND token = 'XkOnI/uRxTsYLfIxK7l/NFswewA1uqiuPfUOy/Kl3fk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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