SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e3b648cede46711013a345c60be5060fe8b305f79d36c168e2c220c31bcd175' 
  AND token = 'vIcfcrrZ3JdEV+4ftazu1quxyW1yHzHc3NlcUDjB1uA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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