SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21b4dc49e6a9fd82fa1b045f17129c54504a41965e6c5c0be749a235d70d955f' 
  AND token = 'HVLwya++OhASy9zBVfnYI4JCYDuEBCFyC4Sgj25ZVm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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