SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd702dc3b35166ef525846f644191139e720b2e9c11346994709e1a7e388650c6' 
  AND token = 'LFcBoh5YxMMagrNjSMrmJUN8c+xeMRZWT+bk/HoCrFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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