SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '502def596ff4dbd5c5e0ae0b1ceb6af39a68ba787e666acfa7afacc62659a1c8' 
  AND token = 'JfTwNKIEpz3UpQJAl6NLs7A2LseWPfBCLKyAK9zP+oU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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