SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c821fd4de453abff4a8adbcdd2931d6d642c4800a52290507669771b86a1554' 
  AND token = 'zILlwd/XPJhArUiQhprkDfypXRXkforZKac9UJ6P6DQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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