SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f5a332bfcb19eaa87727efbf3ba50d47f81afeae734a49928fbd939acfdb5f97' 
  AND token = '9ZWuw5pCAKi1g4NtCNyOxsHaLWiVAsr/gSj0e2LMRa4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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