SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3363c59f0508a63520b3f902167b52d4b2b3173f6357371daadc4e408835915' 
  AND token = 'HXfTW6643MB0f16OwsDlpE4DvM9+bI1/9XBhhKziCbI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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