SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6bb834f4fbfa4e28f8af7cec876ffe257aadac6cc254da0afed919883dfbe683' 
  AND token = 'SLSxJLmA5GoUQbKUzCZCXQAXMeE3WBdqgwn91aqqCqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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