SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3df88127a58ece8ad84076fab0d953bd5794d8aada84373db8fba99458f42b02' 
  AND token = 'R38PtcpfqfrvLhMsCWvAYGezeb2rdViUBC3JtXGB97c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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