SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff8042e63d8991bda015365b7bc78001780e258d6e4a41666c2eda985a6f703b' 
  AND token = 'YdGclOrPFt/u024jHYI961knnbFOHPMuxB7pHc+dTrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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