SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68b48919f803077b627ad1024c3425d448783e25acd6620fb3c952c90f6959f6' 
  AND token = 'x236Fmby5bz9CBU9CfrJ1OMx8OvBPdWKxtsIq4+jJQw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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