SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1844293542e9283b4766693465a6d31f25e75846dee5ff8c0dcc230de061e7d6' 
  AND token = 'FH/+8NxW4KUKcBUYYGoEfhcXZr2lCDmvfoHFawqOWZs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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