SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fd8d819b09b432c88ce340eadd1656f48296f52f314cfd11fc3e851396c379f8' 
  AND token = 'YLotv/tquDTS11WWOXEZTuksqnYU20p3k1A23NidAEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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