SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af88f46b5d5836b9d4098dac0af7855d2d5ef8b99a2de3002a99868947ece2e6' 
  AND token = '2cw4l8XPBgimFYqinpMSTvGpVCBk2cBmhPDKJxD+AqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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