SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3734c78175f59dedf1b443626124b452a3e09c0c7cfeb600e86f99a72e104e65' 
  AND token = 'mrI/ygSzLKpluRwG7tv3ktfmQNAALIQxwdTF7GyKifg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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