SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29b99612e0751517b7b6e58628c555c336099666ddb86c58742f345985c46f08' 
  AND token = 'tbl/hRXsS2gTdxh3VgxaetbVxq4y8XzK+gowtfPTmUU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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