SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf7870505b017bacf336587ccf2a3898f6b67d30ac5834a67c369a9923f0f437' 
  AND token = 'vxLbYSZ1/OIg2qe73cdcdSSBgayKyMJXhlbzVk+IuKs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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