SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '720705c19270836865d39143e980dcc7afcafa2c7da6c14d9b8f5608a727f3e2' 
  AND token = 'TnMXKVlMzPZ+gQS4A36msEo1meL+FFB3+LrEDLvZ3KU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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