SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'eb763a923b974208c3a42b4564ad098fc7da649938a65ea3586af87340f31f2d' 
  AND token = '+eEgpJMtpXrKzDOWNDFS69R4JaUxwjLo7r1mt8vCfUM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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