SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31661c05bea46ef85ce183fa54256703256f59e5cbf8dc77872afff4f49821f3' 
  AND token = 'zY37DvhMRRIAdwcfbwuTkDEPtVgcfZUN+nQ/1U7emjY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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