SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '709986fe21edcbd4f136068b9b88b57c9db3dff4c5a19154637dcb60ec794613' 
  AND token = '8ebfDdi8iXetOX4uvb/GioK3wGFU8VD3+VQSt35b6XM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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