SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d1d5ca847538ffd51d4c1bf441bd2ba187262c3361e661c4356da72d5155a2f' 
  AND token = 'eZn6CPMzQXBDAHT5j3rNmrrBPByEihXEnF7pGOhGWfo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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