SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1240e9421d955cfead41f0f9222b45120736cc51fca48c1f15f56382e3ba641e' 
  AND token = 'ex2UUYRxPfXW2hH3vTySjRqnUJze6y0WmPRd8wTNpT0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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