SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '735cb7beda969adf7da4e15a592b1708f52417a932dc652155f125f5bef3d520' 
  AND token = 'U+8hMkBPHIB6ldopcg1zXywHUvHo5CqGs26e9EmIBUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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