SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '874c5e3bb4483c580327493d9abf409cf866348175b9d2aa6151732d807b6389' 
  AND token = 'JjNiBOVT3e0mMyz+pdXbKA1xLHTOsNjqtaWQNdgqLVI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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