SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '731714639de236e1958df06cf42b2377f2a70814aba898e55a48b41a3c43194c' 
  AND token = 'fdfSse+AvhQjRPfwj8tFwJ0agw90RtxntzVemMDKmZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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