SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3dff9a2995a6eb3227320a96ecc80e4cbb637dd799ed665548a50f2a09dc6ccd' 
  AND token = '5waa+ZKmqvnWkpHligqyzI2SpJvhgsLkx8/NTgTA5f4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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