SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f309e6ebd7e6243871a47185833a078c769a14e8a347496c55cd32215cceb686' 
  AND token = 'tFaHlalKgUOz6MWT1zhJrvl9FlqmrpXzLOD8LHDQtW4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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