SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2176b8f62899316d80514c36e4842bf2533d1ca029bfb9005066c2586197f98d' 
  AND token = 'UpGaiGPwleq4e3FWXNlDvK8PJw6hpmzKTdlFoSObPsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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