SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81606b8630cb710b889591a51ca252b280caf76925eb3821e64308dda3fe41c4' 
  AND token = 'Mw96IVTDjWt/WseekD3DhhY8SgkG/WGPuv8uWqQDnKw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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