SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '840413eef916a9e9eddfcc4119d6d97195905f59565e7459b4fa4fc94b287ebd' 
  AND token = 'l0wcHt3yJwdJo+T+ryRgCW9pKocPqdDijmZv9gWQjLM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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