SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '850c27010f14b2632bebdfead467e44b52889901f03e829f9da99794170cca16' 
  AND token = 'e0aRUpwNDpJVRo/KQWUkTxeQKJijuIFDTcZS+swkmZ4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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