SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90ce92fd14fff03987a266d24915afe2c07eeaad8548bb87d6b2582492253d54' 
  AND token = '7ch4VnKkmjbKeVoidvC53Cs1wMf0UJAOYxSEPdR/iFg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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