SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51cc58b7676a133c76fa2d44466ef912528a480e884a4cc4393ab66fa588657e' 
  AND token = 'CIXBee/2zMqVcdguSG99gh7SQQpl/KJ5fBLMdZl9HjI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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