SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '36c582a20197004856032f496ed15ec169117a42ded75e95b303fa9129c3584f' 
  AND token = '77USHBMNgs/GJibLOnp4y9EpRoC1eJGvd5ztr1JRcpI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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